Kirk & Bistner's Handbook of Veterinary Procedures and Emergency Treatment. 2012 : 551–634. Note: Reference range values listed throughout this section are for general reference only. Test results from individual patients must be compared with the reference range values for the laboratory that performs the test.
Identification of specimens is critical if the right result for a given patient is to get back to the right clinician in a timely manner. The following steps are recommended: 1. Write the animal and client names on each specimen container. 2. Write the animal and client names, species, breed, gender, and date
on the test requisition form. 3. Make sure that the originating clinic name and account number are clearly identified on the form. 4. Clearly mark or write down the needed tests on the form. (Note: Commercial laboratories receive hundreds of samples each day with no test marked!) 5. Indicate the source, if other than a blood sample, on the form. 6. Identify the
tissue or fluid source and clinic ID on all slides submitted for cytology (use a lead pencil to write on the frosted side). Sample collection tubesMost practices use a variety of glass, and occasionally plastic, vacuum tubes (Vacutainer* ) to collect and submit blood, serum, or plasma from individual patients. The tubes are actually designed for collecting blood samples from humans. A variety of tube sizes, each of which maintains a predetermined negative pressure (vacuum) inside, are available. The vacuum facilitates collection of an appropriate volume of the patient's blood to nearly fill the tube. In addition, most of the blood collection tubes contain an additive that will either accelerate or prevent clot formation. Adult (human) tubes are available in 5-mL, 7-mL, 10-mL, and 15-mL sizes. Pediatric (human) tubes, appropriate for use in companion animal patients, are available in 2-mL, 3-mL, and 4-mL sizes. For tubes containing an additive, filling the tube with an appropriate volume of blood is important. Underfilling any tube that contains an additive may alter the sample sufficiently that the test results are adversely affected and may not accurately represent the patient's status. The color of the stopper in the top of the tube indicates the type of additive, if any, and the specific type of tests that can be performed with that sample. For example, do not send serum when plasma is required! Refer to Table 5-1 as a guide for selecting the appropriate tube for the type of test desired. In addition, commercial laboratories generally provide tube selection guidelines. Interpretation of the in-office coagulation screen is outlined in Table 5-2 . Table 5-1Venous Blood Collection Tube Guide*
Table 5-2Interpretation of the In-Office (or Point-of-Care) Coagulation Screen
Special ConsiderationsThe quality and accuracy of test results are influenced by the manner in which samples are collected, stored, and shipped. For example, selecting the improper specimen container (for blood, serum, or plasma) can significantly alter test results; submission of blood in a serum-separator tube (SST) for endocrine testing can adversely affect results because of the gel additive in the tube. In addition, whole blood submitted in ethylenediaminetetraacetic acid (EDTA) for routine hematology begins to deteriorate as soon as the blood is collected. To preserve cell morphology, slides should be made and air-dried immediately after collection of blood. Generally, slides should be submitted unstained and should not be refrigerated, as condensation can also affect cell morphology. The preferred venous blood samples are collected from a large vein and free-flowing blood. Slow blood draws can result in hemolysis, altered cell morphology, and platelet clumping that causes altered hematology and biochemistry test results. To prevent lysis of red blood cells (RBCs), do not force clotted blood out of a syringe and into a collection tube. When filling multiple tubes from a single syringe, always fill the red-topped tube (RTT) first to avoid contamination with liquid tube additives. Even a small amount of EDTA can significantly affect serum chemistries. When filling a lavender-topped tube (EDTA) or light-blue–topped tube (citrate), always add the volume of blood stipulated on the tube. Overfilling or underfilling tubes affects the ratio of additive to sample and can compromise test results. When recovering serum from whole blood by centrifugation, always allow the sample to completely clot before centrifugation. Centrifuging too early can result in a mixed sample that contains both serum and plasma (Box 5-1 ). Box 5-1
EDTA, Ethylenediaminetetraacetic acid; MCH, mean corpuscular hemoglobin; MCHC, mean corpuscular hemoglobin concentration; MCV, mean corpuscular volume; RBC, red blood cell. From IDEXX Reference Laboratories Directory of Tests and Services—2010, Westbrook, Maine, United States, IDEXX Laboratories. Most commercial laboratories recommend collecting a minimum volume of 2.0 mL whole blood for routine biochemical analyses; 2.0 mL of whole blood will yield close to 1.0 mL of serum. Dehydrated patients are expected to have a higher hematocrit (Hct), and therefore a larger volume of whole blood may be required in order to obtain a 1.0-mL sample of serum. When collecting blood from a patient, it is critical to use the following:
Sample storage and transportSeveral types of sample collection or sample submission storage tubes are available. It is critical that the type of blood collection and/or storage tube used meet the requirements of the test as defined by the laboratory. To prepare a sample for storage and transport:
Patient preparationFasting the patient for 8 to 12 hours (an overnight fast with free access to water) is often helpful to reduce the likelihood of lipemia, which may interfere with several tests by falsely increasing or decreasing the results. When applicable, comments about the presence and influence of lipemia and/or hemolysis should appear on the laboratory reports. For special tests, patient preparation may include restriction of food as well as water and certain drugs. It is important to follow the guidance provided in this section regarding patient preparation or to contact the laboratory for specific instructions. Minimizing hemolysisHemolysis during blood drawing can be minimized by adhering to the following recommendations. Procure a nonlipemic (fasted) sample, because lipemia can increase red cell fragility. During phlebotomy, negative pressure created by the vacuum tube or syringe may collapse the lumen of the vein against the needle, thereby crushing numerous red cells. The flutter of the lumen against the needle can be stopped by reducing the negative pressure exerted during collection and by repositioning the needle with slight rotation or deeper insertion. Note: If the patient has lipemic serum or blood after an 8-hour fast, a lipid analysis should be performed on the lipemic serum. The laboratory should be instructed not to clear the sample before determining lipid levels, especially for triglyceride. Excessive negative pressure exerted as the blood enters the vacuum tube or syringe can create hemolysis. This occurs during a slow or difficult collection, because the natural tendency is to use more negative force to enhance blood flow. More patience and “milking” the vein by alternating gentle negative pressure with a short release of all pressure usually solves the problem. Hemolysis often occurs during the transfer of blood from a syringe into vacuum or other tubes. If a small-gauge needle is used, transfer of blood to specimen tubes is slowed, especially if small clots are present. Forcing the blood through a small-bore needle contributes to hemolysis. This problem can be avoided by removing the needle and top of the specimen tube and transferring the blood directly into the open tube. Recapping the tube and aspirating a small amount of air to reestablish negative pressure helps to avoid having caps coming off in transit. Avoiding clots and platelet clumpsThe presence of clots and clumped platelets in anticoagulated blood is most commonly caused by a slow blood draw and the resulting delay in mixing it with the appropriate anticoagulant. If the venipuncture was traumatic, tissue fluid (thromboplastin), activated clotting factors, and hemolysis will quickly promote clot formation. The slight transfer delay when using a syringe for collection can also contribute to this problem. To avoid the formation of clots, do the following:
If the syringe method is selected and a difficult draw is anticipated, the potential for clotting can be minimized by first rinsing the needle and syringe with a small quantity of liquid citrate (blue-topped tube [BTT]) or EDTA (lavender-topped tube). However, the anticoagulant must be emptied from the syringe before proceeding, and care must be taken to match the anticoagulant chosen with the tests to be performed. Even trace amounts of heparin or EDTA will invalidate coagulation testing, whereas EDTA or citrate will alter the accuracy of several chemistry assays. A small amount of heparin contamination is acceptable in most chemistry assays and complete blood count parameters. Platelet clumping in samples from cats is very common and is caused by contact aggregation. An effective method to prevent this clumping has not been found. Applying fresh blood directly to the slide from the syringe and making the blood smear immediately after collection is an effective method of assessing platelet numbers in cats. Submission requirements for rabies suspectsGuidelines for submitting tissue from dead dogs or cats for rabies diagnostic testing vary somewhat from state to state. Contact the State Veterinary Diagnostic Laboratory or Department of Public Health before shipping any samples. Most public health authorities require advance notification about impending submission of samples for rabies testing. Veterinarians should verify the address, paperwork requirements, and shipping requirements before submitting any samples for rabies testing. Caution: Care must be taken during sample preparation to avoid direct personal contact with specimens. Preexposure rabies vaccination is recommended for persons preparing rabies specimens. Sample submission for rabies testing
Packaging requirements for authorized samplesIn the case of a suspect dog or cat, the entire brain must be properly packaged in a standard rabies shipping container (these are often provided at county health departments). Specimens must be accompanied by a completed rabies specimen history form. Forms can often be downloaded from a website designated by the state public health authorities or the diagnostic laboratory. Information requested on the rabies specimen history form
Submission guidelines
Packing and shipping directionsAn acceptable rabies suspect shipping set may include any of the following:
To prepare the specimen for shipping:
Histopathology and cytopathologyHistopathology and cytopathology are among the most important diagnostic tools available for use in clinical practice. Generally, diagnostic specimens are submitted to a commercial laboratory or university where specially trained technologists can prepare and stain the cells or tissue to be interpreted by a pathologist. One critical limiting factor in obtaining diagnostic cytology or histopathology is the quality of the specimen submitted. It is the responsibility of the practice not only to obtain but also to prepare specimens properly before submission and interpretation. This part of Section 5 describes standards for preparing and submitting specimens for cytologic or histopathologic interpretation. Sample collection techniques are described in Section 4. HistopathologyBiopsy TissueTissue specimens for histology must be preserved and transported in formalin (10 parts formalin to 1 part tissue). The ideal tissue specimen is less than an inch thick. Occupational Safety and Health Administration (OSHA) and transportation safety regulations limit the size and quantity of formalin containers that can be shipped. It is strongly recommended that containers supplied by the laboratory or the Federal Aviation Administration (FAA)–approved airline be used; place the container in a Ziploc plastic bag, and then in a second outer bag that contains the requisition. Do not use sample containers that are not approved for formalin use. Samples packaged inappropriately may not be picked up by the courier. Caution: Do not enclose cytology samples in bags containing formalin-fixed tissues because this may alter the cytologic appearance and staining of the cells of interest. Very Large SpecimensSeveral (preferably three or more) representative sections of large tissues or organs should be selected, preserved, and transported for histology. The remainder should be placed in a large plastic container of formalin, refrigerated, and retained in case additional samples are needed. If necessary to ship large tissue specimens to a laboratory, use only containers provided by the laboratory or submit fresh tissue in triple leakproof bags. Tissue Orientation and InformationKnowing the orientation and other facts about the tissue mass is critical for the pathologist. A diagram may be included on the requisition form. Borders and areas of interest on the mass can be marked with colored or numbered sutures. State whether the entire mass has been excised, if all is being submitted, or if the tissue had to be divided into sections before submission. Very Small SpecimensTiny samples, such as endoscopic biopsy specimens, are best preserved if they are first placed in a labeled tissue cassette holder (usually available from the laboratory) and then dropped into formalin. Small biopsy specimens should not be placed in a container with large tissue, because they are easily lost. Do not submit tissue on wooden tongue depressors as the specimen tends to fall off. CytopathologyUsed alone, as a diagnostic screening test for underlying disease, or in conjunction with the surgical biopsy to facilitate rapid assessment of a potentially serious lesion, cytopathology is among the most fundamental and important diagnostic tools used in clinical practice. Cytopathology is not a clinical discipline restricted to the realm of board-certified clinical pathologists. Several continuing education short courses and laboratories on diagnostic cytopathology are offered at major conferences throughout the United States. In addition, excellent textbooks, with abundant color plates, are available to facilitate cytologic interpretation of specimens collected from dogs and cats. Cytologic preparations are perhaps most useful for distinguishing details between cell types (e.g., mesenchymal versus epithelial) and cellular activity (e.g., inflammation versus neoplasia). Detection of intracellular versus extracellular organisms can provide immediate clues, without waiting for organisms to be cultured, about the nature of the disease. Noninflammatory lesions can generally be distinguished as benign or neoplastic. Although it is the responsibility of the individual clinician to understand personal limitations when interpreting cytopathology on individual patients, there is one special advantage that the clinician does have over the pathologist—familiarity with the patient's health status and the nature of the lesion or disease under consideration. Described here are guidelines for preparing and submitting samples for cytologic interpretation (see Section 4 for sample collection techniques). Whether samples are sent to a commercial laboratory or a university, or are interpreted within the practice, the recommendations that follow are important when preparing a high-quality specimen. Note: The accuracy of interpreting cytopathologic specimens is dependent on four key variables:
Fine-Needle AspirationIndicationsFNA involves the use of a syringe and needle to extract cells from a palpable lesion. Most commonly, FNA is performed on cutaneous and subcutaneous lesions. However, with the increasing use of ultrasound in private practice, it may not be necessary to actually “palpate” a lesion in order to extract diagnostic cytology (e.g., ultrasound-guided hepatic or splenic aspirates). Additional experience and training are essential when attempting to perform ultrasound-guided FNA. Sample PreparationBecause sample size typically is small, the cells collected are discharged directly onto a dry, clean slide and allowed to rapidly (within 5 to 10 seconds) air-dry. It is recommended that the needle tip actually contact the slide as the aspirate is discharged rather than blowing the sample over the slide. If clear fluid is inadvertently recovered, the FNA should be reattempted from the peripheral limits of the lesion. An extremely small harvest of cells can be sprayed directly on the slide, remain untouched, and allowed to air-dry. If the volume recovered allows placement of a formed drop onto the slide, the sample should be spread over the surface of the slide, before to air-drying, in the same way that a peripheral blood smear is prepared. Staining OptionsOnce the sample has air-dried (rapidly), use of a quick Romanowsky-type (Wright) stain is appropriate. Alcohol fixation is not recommended if the specimen is to be reviewed and interpreted immediately. Alternative stains, such as new methylene blue (wet mount), Gram stain, Giemsa stain, or Wright-Giemsa stain, can be used in practice as dictated by cytologic objectives. FNA specimens mailed to an outside laboratory typically are air-dried and left unstained. Some laboratories recommend that the specimen be immersed in methyl alcohol for a few minutes before sending, although this additional step seems to be optional. Common MistakesLow cell harvest, high cellular density on the slide (e.g., the result of making a “bad” slide or failing to adequately disperse the sample), and obtaining nondiagnostic material are the three most common mistakes when obtaining samples for diagnostic cytopathology. Contamination of the “wet” (not yet air-dried) sample with water, alcohol, or stain can create artifacts that will compromise the diagnostic value of the specimen. Excessive blood or tissue fluids may profoundly dilute the diagnostic sample, making interpretation difficult or impossible. Exfoliative Cytology (“Impression Smear”)IndicationsExfoliative cytology is made from a clean surface of exposed lesions or from the surface of tissue collected during biopsy. Preparations made from the cut surface of fresh biopsy specimens or postmortem tissues provide the greatest diagnostic yield. Sample PreparationFor prevention of one of the most common mistakes, excessive tissue fluid or blood is absorbed from the cut surface (using a scalpel blade) of the specimen before the attempt to exfoliate cells on a slide. Clean, high-quality absorptive paper (such as filter paper) works well, and fragments of paper will not be left on the specimen. Once excess fluid has been absorbed from the surface, the specimen is gently grasped and allowed to make gentle contact with a clean slide. The actual weight of the specimen is usually sufficient; it is usually not necessary to press the specimen onto the slide. After multiple contacts with the slide have been made, the sample is rapidly air-dried. Staining OptionsOnce the sample has air-dried (rapidly), use of a quick Romanowsky-type (Wright) stain is appropriate. Alcohol fixation is not recommended if the specimen is to be reviewed and interpreted immediately. Alternative stains, such as new methylene blue and Gram stain (wet mounts), Giemsa stain, or Wright-Giemsa stain, can be used in practice as dictated by cytologic objectives. Common MistakesExcessive or rough handling of the specimen before attempting exfoliation will compromise the quality of the specimen. In addition, excessive blood or tissue fluid on the cut surface of the tissue may effectively “dilute” the diagnostic cells in the specimen, making interpretation difficult. When additional pressure is used to exfoliate cells or the specimen is rubbed across the slide, individual cells are likely to rupture and smear, rendering the sample nondiagnostic. Failure to obtain adequate numbers of diagnostic cells is more likely to be the consequence of the type of tissue being examined than poor technique. Epithelial tissues (liver, spleen, adenoma, carcinoma) tend to exfoliate abundant numbers of cells when applied to a slide. In contrast, mesenchymal cell tissues (fibrosarcoma, chondrosarcoma) tend not to exfoliate well. Diagnostic yield of cells from mesenchymal tissue may be so low as to warrant submission of fixed tissue for histopathologic examination. Swabs, Scrapings, Washings, or BrushingsIndicationsA variety of techniques are available to collect cytologic specimens from the upper and lower respiratory tract, conjunctiva, ear canals, and vaginal mucosa. In most cases, cytologic objectives focus on the recovery and identification of infectious organisms (e.g., mites, bacteria). Section 4 describes the various techniques of sample collection from these locations. Sample PreparationSkin scrapings and ear swabs for diagnosis of infectious agents, and occasionally neoplasia, are perhaps the most common samples used in practice to collect diagnostic specimens. Gentle handling of the specimen once collected is the rule when attempting to exfoliate diagnostic cells or organisms. In addition, it may not be necessary to air-dry or apply a stain, depending on the samples collected (e.g., skin scrapings or ear swabs for mites). Samples collected from washings vary considerably in the cell harvest, the consistency of the fluid recovered, and the quality of the diagnostic specimen. In some cases, fluid recovered from washings (e.g., bronchoalveolar lavage, transtracheal aspiration) will require centrifugation to acquire sufficient numbers of diagnostic cells. The supernatant (fluid portion) of the sample is discarded. The cells recovered may be resuspended in one or two drops of sterile saline or a volume of saline equal to the volume of specimen remaining in the centrifuge tube. A pipette is used to apply a sample of the fluid to a slide. The sample is distributed over the slide in the same way that a peripheral blood smear is prepared. The slide is air-dried and stained. In other cases, the sample collected from cytologic washings will be highly cellular and may be applied directly to a slide, air-dried, and stained. Samples collected from brushings normally are obtained with specially made cytology brushes designed for use during endoscopy. Although small “pinch” biopsies are preferred, occasionally the use of a brush may be the only practical option. Cytologic specimens collected by brushing tend to be especially low in yield. Furthermore, the additional manipulation required to extract cells from the brush and onto a slide for examination tends to yield specimens of poorer quality. Cells obtained during brushing may be applied directly to a clean slide, air-dried, and stained. In other cases it may be preferable to wash the brush in a centrifuge tube containing a small volume (<1.0 mL) of sterile saline. The suspended cells may be applied directly to a slide, distributed, and then air-dried and stained. It may be necessary to centrifuge the sample (as described for washings previously) before preparing the sample. Staining OptionsGenerally, the same staining options previously described apply to specimens collected from washings or brushings. Samples collected from skin scrapings typically are suspended in oil or hydrogen peroxide on the slide and examined “wet” without the use of additional stain. Swabs, especially from ears, may be stained with a quick Romanowsky-type stain or a Gram stain (wet mount) to facilitate identification of organisms. Common MistakesSamples collected from skin scrapings and swabs tend to be relatively high in yield when diagnostic cells or organisms are present. Cells collected from washings and brushings are usually collected during endoscopic procedures; the yield of diagnostic cells can vary, depending on the extent of the lesion as well as the skill of the individual performing the procedure. Body FluidsIndicationsThe accumulation of fluid in either the pleural space or the abdomen, or in both, justifies attempts to remove fluid for diagnostic cytology. The volume of sample can be difficult to determine but ideally would be 2 to 3 mL of fluid collected by needle and syringe (centesis) under sterile conditions. Smaller samples of joint fluid and cerebrospinal fluid (CSF) are also collected for chemical and cytologic analysis. Any fluid recovered should be examined for color, consistency, total nucleated cell count, and protein concentration as well as for morphology of the cells recovered. Other chemistries (e.g., creatinine, amylase) can be determined depending on the nature of the fluid recovered and the patient's condition. Sample PreparationBecause the volume of fluid obtained may be large and the concentration of cells in the fluid recovered may be low, centrifugation is indicated to concentrate cells in small aliquots of fluid. After centrifugation and removal of the supernatant, cells can be resuspended in 1 to 2 drops of sterile saline or supernatant. Suspended cells should be distributed directly on a slide, allowed to air-dry, and stained. When submitting fluids or washes to a commercial laboratory, it is recommended to place fluid samples into a sterile tube without clot activator (e.g., red and dark gray tube; see Table 5-6 ) or a (preferred) lavender-topped tube (which contains EDTA). Samples submitted in EDTA cannot be used for bacterial culture. Do not submit samples in an SST, as these tubes contain a clot activator. Table 5-6Hemostasis Reference Range Values
Note: It is important not to delay processing of cytologic samples recovered from body fluid. The longer cells are allowed to remain in suspension, the greater the opportunity for morphologic changes of cells to occur. Spinal fluid must be processed within 30 minutes of collection because of the fragility of cells in CSF. Furthermore, conventional centrifuges may damage any cells collected. Because of the complexities associated with processing of CSF for cytopathology, most samples are evaluated within specialty or referral hospitals. Staining OptionsAir-dried cytologic preparations can be stained in the same manner described previously. Common MistakesAttempting to evaluate uncentrifuged cytologic specimens collected from body fluids can result in a low yield of diagnostic cells and may compromise the study. Allowing the cells to remain in the fluid for an extended period of time before making the cytologic preparations may significantly alter the morphology of individual cells, making interpretation difficult or impossible. Furthermore, the presence of peripheral blood in any sample collected from a body cavity must be distinguished from contamination associated with the sampling technique versus a primary bleeding disorder. When submitting slides with tissue fixed in formalin, do not package slides with the formalin vial. Even small amounts of formalin can significantly disrupt cell morphology. Bone MarrowIndicationsCytologic examination of a bone marrow aspirate is an especially valuable tool in the assessment of patients with persistent anemia, particularly nonregenerative anemia, abnormal numbers (either high or low) of leukocytes, thrombocytopenia, any blood dyscrasia detected in peripheral blood, and any combination of these findings. Bone marrow specimens will yield the most information if both a core biopsy and aspirate slides are submitted. The biopsy specimen should be cut first, and the core placed in a tissue-processing cassette, labeled, and dropped into a formalin container. The aspirate needle can then be placed into the same puncture site as the biopsy needle. (Bone marrow biopsy and aspiration collection techniques are described in Section 4). Thrombocytopenia is not necessarily a contraindication to performing bone marrow aspiration. Assuming normal platelet function, bone marrow aspiration is indicated even when platelet counts are extremely low (e.g., 5000 platelets/mm3). We have, however, observed persistent bleeding and large hematoma formation at the site of aspiration in dogs with platelets counts of less than 3000 platelets/mm3 in peripheral blood. Sample PreparationIn most patients undergoing bone marrow aspiration, sufficient numbers of platelets will be present in the sample to justify routine use of an anticoagulant. Before collection of the sample, a few drops of 4% EDTA are placed in the center of a watch glass. The same 12-mL syringe used to draw the EDTA is used to collect the sample. This syringe will contain a small amount of EDTA. Collection of marrow is typically limited to 0.5 mL. Larger volumes may cause hemodilution of the sample, making interpretation difficult. On withdrawal of the appropriate volume, the sample is immediately added directly to the EDTA and mixed thoroughly. A glass pipette can be used to transfer the aspirated marrow onto a clean, dry slide. Other techniques are described in Section 4. Using the same technique to distribute peripheral blood for a differential count will suffice. The sample is allowed to air-dry. Staining OptionsBone marrow staining routinely entails use of a quick Romanowsky-type stain. Alternatively, when transporting slides to a laboratory, do not apply any staining. Ensure the slides do not make contact with formalin-fixed samples; do not refrigerate slides. Special staining, usually performed by a commercial or university laboratory, may be indicated when looking for the presence of iron stores or specific types of organisms. Common MistakesIf the bone marrow contains functional platelets, failing to quickly transfer the aspirate into the EDTA can result in clot formation. The presence of clots is likely to entrap diagnostic cells, making interpretation difficult or impossible. Hemodilution and an excessive volume of EDTA are also common mistakes that can compromise the quality of the smears. Other complications usually are caused by errors in the technique of making the slide. For example, failing to adequately distribute the sample across the slide can result in n unusually thick preparation. Bone marrow aspirates taken from the head of the humerus can become contaminated with joint fluid, making the sample completely unusable. Biochemistry—routineThe ability to obtain a comprehensive biochemical profile, and to do so quickly and inexpensively, has made such testing a routine part of the clinical workup for the companion animal patient. Clearly, the biochemistry profile greatly expands the clinician's ability to assess the patient with a history of clinical illness. In addition, it is now feasible to obtain a biochemical profile on seemingly healthy patients as part of a routine “wellness examination.” This section discusses those analytes offered by most clinical laboratories performing companion animal (dog and cat) biochemistry profiles. Although specific analytes included on panels vary among laboratories, any individual test not discussed here is likely to be found in the portion of this section entitled Special Diagnostic Tests and Test Protocols. The following criteria are applicable to all samples in which blood, serum, or plasma is collected and for which a routine biochemistry profile or special laboratory test is requested. Analyte or test name (synonyms)The name of the individual chemical analyte being measured (e.g., alkaline phosphatase) is followed in parentheses by common abbreviations used by laboratories when reporting results (e.g., SAP or alk phos). In some cases the name of the test is presented rather than the actual chemical being tested for (e.g., ACTH stimulation, in which cortisol is the actual analyte measured). NormalRepresentative reference range values for normal adult dogs and cats are listed with each analyte. In addition, Table 5-3, Table 5-4, Table 5-5, Table 5-6, Table 5-7 summarize reference ranges for dogs and cats. Table 5-3Hematology Reference Range Values
Table 5-4Biochemistry Reference Range Values
Table 5-5Urinalysis (Voided Sample) Reference Range Values
Table 5-7Blood Gas Analysis—Arterial Reference Range Values
Note: Reference range values listed throughout this section are for general reference only. Test results from individual patients must be compared with the reference range values of the laboratory that performs the test. Patient preparationAny unique patient preparation parameters should be followed before the sample is collected. For routine biochemistry profiles, an 8- to 10-hour fasting period is recommended when feasible. When performing routine profiles on normal patients, it is preferable to collect samples in the morning. Owners are instructed to withhold food and water after midnight on the day the blood sample is to be collected. CollectThis section stipulates the type and volume of sample to be collected, as well as the type of collection tube to be used. For routine biochemistry, collecting at least 2.0 mL of whole blood in an RTT (or SST) is required to obtain the minimum 1.0 mL of serum required for sample analysis. Dehydrated patients have a higher Hct, and a larger volume of whole blood may be required to obtain 1.0 mL of serum. SubmitThis section stipulates the type and volume of sample that is to be submitted for analysis. Also, the type of vial or container in which the sample should be shipped is specified. Unless specified in the protocol (e.g., polymerase chain reaction [PCR] analyses), do not store or ship samples as whole blood; instead, separate whole blood from serum before shipping or place blood in an appropriate SST. Serum samples should be shipped in a sterile RTT. Freezing of the sample is not required for routine biochemistry profiles. InterpretationEach analyte and test procedure is described separately. For each analyte, an interpretive summary of the significance of an abnormal (either elevated or decreased) value is provided. Test results for any analyte must be interpreted after consideration of other laboratory results (e.g., hematology, urinalysis) as well as the patient's medical history and physical examination findings. InterferenceThis section stipulates common interfering substances and factors and indicates, when known, if the interference will falsely elevate or lower test results. Samples that are lipemic, icteric, and/or hemolyzed may cause test interference with individual analyte assays, resulting in unreliable test results. Interference may be positive (false increased test results) or negative (false decreased test results). The degree and type of interference vary depending on the test methodology used. In the final reports, most laboratories provide details pertaining to known or potential interfering factors. ProtocolIf indicated, the protocol stipulates specific test procedures or shipping requirements necessary to obtain the most valid results. For routine biochemistry profiles, other than recommended fasting of the patient, no specific test protocol is indicated. A detailed description is provided for special laboratory tests that require specific patient preparation or adherence to a unique test protocol. Routine biochemical testingAlanine aminotransferase (Alt; formerly SGPT)Normal16 to 73 international units/L (dog); 5 to 134 international units/L (cat) InterpretationALT is used in the assessment of liver disease (not a test of liver function). Increased values indicate hepatocyte injury and leakage of intracellular enzymes, such as could occur in acute hepatitis, hepatic trauma, neoplasia (occasionally), and cirrhosis. Decreased values may be noted in end-stage liver disease. AlbuminNormal2.8 to 4.0 g/dL (dog); 3.0 to 4.2 g/dL (cat) InterpretationEvaluated with total protein and globulin. This test is important in the assessment of hydration status, renal disease, gastrointestinal (GI) disease, liver function, and selected chronic infectious diseases. Increased values generally support dehydration; a commensurate increase in globulin and total protein should be expected. Decreased values suggest abnormal loss (GI tract or renal) and decreased production (protein-restricted diet, malnutrition, liver disease). Values in healthy young dogs and cats (<3 months of age) are normally lower than those in adult animals. Albumin/globulin ratio (A:G)Normal0.6 to 2.0 (dog); 0.4 to 1.5 (cat) InterpretationThe A:G should not be interpreted without consideration of the concentration (g/dL) of both albumin and globulin. Further characterization of serum proteins can be obtained with serum protein electrophoresis. An increased A:G is considered to be clinically insignificant because it represents elevated albumin and/or decreased globulin. Alternatively, a decreased A:G indicates decreased albumin and/or increased globulin and may indicate renal or GI loss of albumin, certain neoplasms, or chronic infections. Serum alkaline phosphatase (SAP or “alk phos”)Normal15 to 146 international units/L (dog); 0 to 96 international units/L (cat) InterpretationSAP is routinely used to assess obstructive liver and/or biliary tract disease (not a test of liver function). Increased values are normal in young dogs and cats (<3 months of age) (reflecting bone growth). In adults, increased values may indicate biliary obstruction or cholestasis, hepatitis, hepatic lipidopathy, destructive bone lesions (osteosarcoma), hyperphosphatemia, and acute pancreatitis. Corticosteroid therapy will induce SAP, causing significant elevations in the absence of cholestasis. AmylaseNormal347 to 1104 international units/L (dog); 489 to 2100 international units/L (cat) InterpretationIncreased value indicates pancreatitis, especially in patients with evidence of vomiting and abdominal pain. Amylase clearance is dependent on normal renal function; patients with compromised renal function (chronic renal failure) are likely to have abnormally elevated amylase not associated with pancreatic disease. Pancreatic lipase immunoreactivity (PLI) may be helpful in assessing pancreatitis in dogs and cats (see under Special Diagnostic Tests and Test Protocols). Anion gapNormal16.3 to 28.6 (dog); 12 to 24 (cat) InterpretationThe anion gap is a laboratory calculation (Na − [CL + HCO3 −] = anion gap) used to assess quantities of unmeasured cations (Ca, Mg) and anions (proteins, sulfates, phosphates, and certain organic acids). A high anion gap suggests metabolic acidosis (ketoacidosis, lactic acidosis). Other causes of metabolic acidosis (e.g., renal tubular acidosis) may have a normal anion gap. Hypoalbuminemia is the most common cause of a low anion gap. Other causes include hypernatremia, certain gammopathies (myeloma), and severe hypercalcemia. There are numerous causes for false high and low anion gap results. Aspartate aminotransferase (formerly sgot)Although sometimes reported in companion animal laboratory profiles, aspartate aminotransferase (formerly SGOT) values are not considered to have clinical significance in either the dog or the cat. Bicarbonate ()Normal24 to 26 mEq/L (dog); 22 to 24 mEq/L (cat) InterpretationBicarbonate measurement usually is included as a component of blood gas and/or electrolyte panel. Levels are increased with metabolic alkalosis (and with compensated respiratory acidosis) and decreased with metabolic acidosis (and with compensated respiratory alkalosis). BilirubinNormal0 to 0.2 mg/dL (dog); 0.1 to 0.5 mg/dL (cat) InterpretationIncreased value (hyperbilirubinemia) may be associated with icterus or jaundice, reflects accumulation of bilirubin in serum, and may indicate intravascular hemolysis, compromised bile excretion, biliary tract obstruction (intrahepatic or extrahepatic), and primary hepatic disease affecting bile excretion. Blood urea nitrogen (BUN)Normal8 to 27 mg/dL (dog); 15 to 35 mg/dL (cat) InterpretationNote: Abnormally elevated BUN (azotemia) does not define “uremia.” Increased BUN indicates decreased renal clearance of nitrogenous waste (dehydration, renal failure, urinary tract obstruction). An elevated BUN is not indicative of renal disease unless interpreted in light of other parameters (e.g., urine specific gravity, serum creatinine, history of increased water consumption or increased urination). Decreased BUN indicates increased renal excretion of nitrogenous waste (diuresis) or decreased protein intake (malnutrition, low-protein diet) or decreased production (portosystemic shunt). Calcium (CA)Normal9.2 to 11.6 mg/dL (dog); 7.5 to 11.5 mg/dL (cat) InterpretationWarning: Levels ≤7 mg/dL dogs and cats may result in tetany; sustained levels >12 mg/dL may cause renal damage subsequent to calcium deposition. Increased levels are associated with primary hyperparathyroidism, pseudohyperparathyroidism (paraneoplastic syndrome associated with neoplasia, especially lymphosarcoma and perianal carcinoma), metastatic bone disease or primary bone tumors, hypervitaminosis D (chronic), hyperthyroidism (in cats), Addison disease (hypoadrenocorticism), and acromegaly. Hypercalcemia may be idiopathic in some animals. Decreased values are associated with any condition causing low total protein and albumin levels (most serum calcium is albumin-bound). Serum ionized calcium (iCa) is indicated in assessing any patient with significant, unexplained hypercalcemia or hypocalcemia. Other causes of decreased calcium include conditions that cause elevated phosphorus levels (e.g., renal insufficiency, hypoparathyroidism), acute pancreatitis, intravenous fluid administration, and renal tubular acidosis. See also Calcium, Ionized (iCa). Chloride (CL)Normal104 to 117 mEq/L (dog); 113 to 122 mEq/L (cat) InterpretationIncreased Cl is associated with dehydration as well as intravenous saline administration. Decreased Cl can be associated with overhydration, Addison disease (hypoadrenocorticism), burns, metabolic alkalosis, syndrome of inappropriate secretion of antidiuretic hormone (ADH), and certain types of diuretic therapy.
Cholesterol (CH)Normal138 to 317 mg/dL (dog); 42 to 265 mg/dL (cat) InterpretationIncreased CH (hypercholesterolemia) is most commonly found in hyperlipidemic patients and reflects extreme elevations of triglyceride rather than a primary underlying metabolic disorder affecting CH metabolism. In dogs, hypercholesterolemia is inconsistently associated with hypothyroidism and hyperadrenocorticism (Cushing syndrome). Hypercholesterolemia has limited diagnostic significance. Decreased CH (hypocholesterolemia) has not been found to be of diagnostic significance in the dog and cat but has been observed with hypoadrenocorticism. Creatine kinase (ck; formerly cpk)Normal48 to 380 international units/L (dog); 72 to 481 international units/L (cat) InterpretationIncreased CK indicates increased skeletal muscle activity or destruction (myopathy or rhabdomyolysis), inflammation or infection (myositis), or widespread muscle trauma. No diagnostic significance has been associated with a decreased CK. Creatinine (cr)Normal0.5 to 1.6 mg/dL (dog); 0.5 to 2.3 mg/dL (cat) InterpretationIncreased Cr is an important indicator of glomerular filtration and occurs with renal insufficiency and urinary tract obstruction; shock, severe dehydration, and untreated congestive heart failure may result in increased Cr owing to decreased renal blood flow. Rhabdomyolysis will also cause increased Cr. Pathologic causes of decreased Cr are uncommon but may occur in severe debilitation or disease that causes extreme decreases in muscle mass. Cr is less influenced by diet than by BUN. γ-Glutamyltransferase (ggt; gamma gt [gGT])Normal3 to 8 international units/L (dog); 0 to 10 international units/L (cat) InterpretationParameters causing increased and decreased GGT typically parallel SAP in the presence of underlying liver pathology, especially cholestasis, but not in patients with destructive bone disease. GGT is commonly elevated in cirrhosis and (obstructive) hepatic or biliary tract disease. Extreme elevations of GGT have been associated with metastatic liver disease in humans; a similar association has not been reported in animals. GlobulinNormal2.0 to 4.1 g/dL (dog); 2.8 to 5.3 g/dL (cat) InterpretationGlobulin is a component of total protein that must be interpreted with albumin. Increased value (hyperglobulinemia) may reflect dehydration (albumin and total protein also increased), chronic inflammation, chronic infection, or myeloid neoplasia (albumin may be abnormally decreased). Serum protein electrophoresis is indicated to characterize the nature of the globulin increase. Decreased value (hypoglobulinemia) typically indicates decreased protein intake (low protein diet or malnutrition) or decreased globulin production (neoplasia). GlucoseNormal73 to 116 mg/dL (dog); 63 to 150 mg/dL (cat) InterpretationIncreased value (hyperglycemia) indicates decreased glucose metabolism (insulin deficiency or diabetes mellitus). Note: Normal cats may experience transient “stress hyperglycemia” with values as high as 350 mg/dL (typically, glycosuria is absent). Decreased value (hypoglycemia) indicates excessive usage of glucose (insulin-secreting tumor) or severe illness (sepsis). LipaseNormal22 to 216 international units/L (dog); 0 to 222 international units/L (cat) InterpretationIncreased lipase is most commonly associated with acute pancreatitis. Certain neoplasms have been reported to cause extreme elevations of lipase in the absence of pancreatic disease. There is no clinical significance associated with decreased lipase. Phosphorus (P)Normal2.0 to 6.7 mg/dL (dog); 2.7 to 7.6 mg/dL (cat) InterpretationIncreased P is normally present in young, growing dogs and cats (associated with increase SAP activity). Abnormal elevations are most likely to occur in patients with chronic renal failure or hypoparathyroidism. Improper sample handling (hemolysis) can cause elevations in P. Decreased P is expected in patients with primary hyperparathyroidism (with increased calcium), renal tubular acidosis, and Fanconi syndrome. Several systemic illnesses may be associated with decreased P. Warning: Values of 1 mg/dL or less may be associated with neuromuscular abnormalities and cardiac arrhythmia. Potassium (K+)Normal3.9 to 5.2 mEq/L (dog); 3.3 to 5.7 mEq/L (cat) InterpretationIncreased value (hyperkalemia) may indicate mineralocorticoid deficiency (Addison disease or hypoadrenocorticism) but must be interpreted with serum sodium and an adrenocorticotropic hormone (ACTH) stimulation test. Numerous causes of decreased potassium are recognized. GI and renal losses are the most common and most significant. Persistent hypokalemia warrants significant efforts to determine the underlying cause(s). Warning: Potassium levels greater than 7.5 mEq/L may cause cardiac arrhythmias (profound bradycardia) and death. Potassium levels less than 2.5 mEq/L may cause profound weakness. Sodium (na+)Normal147 to 154 mEq/L (dog); 147 to 165 mEq/L (cat) InterpretationIncreased value (hypernatremia) may result from excess dietary consumption or severe dehydration. Decreased value (hyponatremia) may indicate mineralocorticoid deficiency (Addison disease or hypoadrenocorticism) but must be interpreted in light of other tests (e.g., serum osmolality, potassium, ACTH stimulation test). Persistent diuresis caused by drugs (furosemide) or an inherent medical disorder (nephrotic syndrome) can deplete serum sodium to significantly low levels. Depending on the laboratory methodology, pseudohyponatremia may occur in patients with profoundly lipemic serum. Total protein (TP)Normal5.5 to 7.2 g/dL (dog); 5.4 to 8.9 g/dL (cat) InterpretationTP must be evaluated with constituent proteins albumin and globulin. Increased TP (hyperproteinemia) may indicate dehydration (elevated albumin and globulin) or extreme elevations in globulin (chronic inflammation, infection, neoplasia, especially myeloma). Decreased TP may indicate increased protein loss (especially albumin), chronic malassimilation or maldigestion, starvation, or chronic illnesses (tumor cachexia). Triglyceride (TG)Normal19 to 133 mg/dL (dog); 24 to 206 mg/dL (cat) InterpretationTG is normally increased in any animal during the postprandial state (with 6 hours after a meal). TG is the cause of gross lipemia when concentrations exceed approximately 500 mg/dL. Increased TG (in the fasted patient) is associated with familial hypertriglyceridemia, a condition most often reported in Miniature Schnauzers (other breeds and mixed breeds may be affected) born in the United States (the condition has not been described in Miniature Schnauzers in Europe or the United Kingdom) and certain lines of mixed-breed cats. There is no clinical significance associated with decreased TG in either the dog or the cat. Special diagnostic tests and test protocolsThis section includes advanced biochemical laboratory tests not typically included in routine companion animal medicine laboratory profiles. These tests are selected on the basis of abnormal findings revealed during routine physical examination and laboratory profiling. Additional special laboratory tests and test procedures can be found in the organ system–specific sections that follow. Note: Throughout the Special Diagnostic Tests and Test Protocols section, the following information is provided, where appropriate, for each laboratory test described:
Acetylcholine (ACH) receptor antibodySee Immunology. Adrenocorticotropic hormone (ACTH) stimulation testSee Endocrinology. Ammonia (NH3) (fasting ammonia)Normal45 to 120 mcg/dL (dog); 30 to 100 mcg/dL (cat) Patient PreparationOvernight fast CollectWhole blood, 2.0 mL minimum, in EDTA (purple-topped tube) or in heparin SubmitPlasma, 1.0 mL minimum InterpretationDecreased levels of ammonia are not considered clinically significant. Elevated ammonia levels support the diagnosis of underlying, significant liver disease. This test generally is considered a liver function test and usually is performed to support a diagnosis of hepatic encephalopathy. Fasting ammonia and ammonia tolerance tests are uncommonly performed today because of sample instability and specimen handling requirements. These tests have largely been replaced by pre– and post–bile acid assay. InterferenceHemolysis; elevated BUN; glucose values greater than 600 mg/dL. NH3 is unstable if not frozen at - 20° C.
Limiting FactorsIdeally, blood should be collected in a sealed, cold glass collection tube, centrifuged immediately, and plasma analyzed within 20 minutes of collection. Alternatively, plasma can be stored for up to 48 hours if frozen immediately after collection and kept frozen until time of analysis. Ammonia tolerance testNormal Resting Values45 to 120 mcg/dL (dog); 30 to 100 mcg/dL (cat) Note: Minimal change should be detected after oral challenge because clearance is nearly 100% after a single pass through the liver. Patient PreparationOvernight fast CollectWhole blood, 2.0 mL minimum, in EDTA (purple-topped tube) or in heparin SubmitPlasma, 1.0 mL minimum, for each prechallenge and postchallenge sample. InterpretationElevated ammonia levels support the diagnosis of underlying, significant liver disease. This generally is considered a liver function test and is usually performed to support a diagnosis of hepatic encephalopathy. Fasting ammonia and ammonia tolerance tests are uncommonly performed today because of sample instability and specimen handling requirements. These tests have largely been replaced by pre– and post–bile acid assay. InterferenceHemolysis; elevated BUN; glucose values greater than 600 mg/dL. NH3 is unstable if not frozen at - 20° C. Limiting FactorsIdeally, blood should be collected in a sealed, cold glass collection tube, centrifuged immediately, and plasma analyzed within 20 minutes of collection. Alternatively, plasma can be stored for up to 48 hours if frozen immediately after collection and kept frozen until time of analysis. ProtocolTwo plasma samples are required. The first is a baseline sample. The second sample is collected 30 to 45 minutes after administration of ammonium chloride (NH4Cl) at 100 mg/kg body weight as an oral 5% solution in approximately 20 to 50 mL of saline. NH4Cl is also available as a powder that can be administered orally, at the same dose, which lowers the risk of vomiting or aspiration. Bile acidsNormal (Dog and Cat)Prefeeding, ≤7 µmol/L; postfeeding, ≤15 µmol/L Patient Preparation12-hour or overnight fast before collection of the prefeeding sample CollectWhole blood, 2.0 mL minimum, in RTT for each sample collected SubmitSerum, 1.0 mL minimum, for each sample submitted InterpretationBile acids are indicated for the assessment of hepatobiliary disease in nonicteric patients. There is no value in performing this test in patients that are icteric. Hepatobiliary disease (e.g., portosystemic shunt) is supported with either a prefeeding sample of more than 7 μmol/L or a postfeeding sample of more than 15 µmol/L. Note: Reference range values may vary among different laboratories. InterferenceLipemia; icterus; hemolysis. Results in patients that vomit the meal before collection of the 2-hour postfeeding sample cannot be expected to be reliable. Individual variations in gastric emptying and absorption can result in discordant results (e.g., the prefeeding sample is higher than the postfeeding sample). Such results are not reliable, and the test should be repeated. Protocol
Blood gases (arterial and venous)The values represented in the following table are expected from patients breathing room air. Normal
Patient PreparationPatients breathing 100% oxygen at the time of sample collection are expected to have different results from those of patients that are breathing room air during sample collection. Note the conditions under which the sample was collected. CollectWhole blood, either arterial or venous, depending on the assessment required SubmitSample cannot be stored. Immediate testing is required for reliable results to be obtained. InterpretationTco2 is synonymous with HCO3 − in patients breathing room air. The overall interpretation of venous and/or arterial blood gas results will vary considerably depending on the patient's health status. Several variations in test results are possible. The clinician should consult appropriate references to interpret results from individual patients (see Section 1). InterferenceThe test should be performed immediately after collection of the sample. Delays could cause significant abnormalities in actual results. Exposure of the sample to room air (bubbles within the sample) may cause Pco2 to decrease, whereas pH and Po2 may increase. Blood typingSee page 593 in this section. Body fluids (submitted for chemistry analysis)Patient PreparationWhen feasible, the skin over the site selected for centesis should be shaved and surgically prepared before sample collection is attempted, to avoid contamination of either the sample or the body cavity from which the sample is collected. Collect1 to 2 mL, minimum, by direct centesis of body cavity or fluid-filled compartment SubmitCentrifugation of whole blood contamination is indicated to remove particulate material (e.g., blood cells, cellular debris) when prompt evaluation of a specimen is not possible. InterpretationAny biochemical analyte determined in serum or plasma may be assayed in body fluid—for example, amylase, lipase (pancreatitis), urea nitrogen, creatinine (ruptured bladder), glucose, lactate. InterferenceBlood and blood components, bilirubin, bile, and urine may significantly interfere with test results. Centrifugation of the sample (blood contamination) may be necessary before any biochemistry test is performed. Brain natriuretic peptide (BNP, proBNP, NT proBNP)Normal<800 pmol/L (dog); <50 pmol/L (cat) Recommendations for the normal reference ranges of proBNP are subject to change as new information is published on this assay. Refer to the reference laboratory for the latest recommendations on interpreting test results for the dog and cat. CollectAnticoagulated whole blood, 2.0 to 3.0 mL; use a lavender-topped tube. The sample must be centrifuged and plasma separated within 30 minutes after collection. Plasma sample should be inverted several times after separation. Submit1.0 mL plasma; must be submitted in a special transport tube provided by the laboratory (IDEXX Laboratories, Westbrook, Maine). InterpretationCurrent studies do show, in both dogs and cats, that elevated levels of proBNP correlate well with existing heart disease, particularly cardiomyopathy. Test results must be considered with information derived from a clinical evaluation and cardiac examination, including electrocardiography and echocardiography. Ongoing studies are evaluating the value of proBNP levels in monitoring individual response to treatment for various heart diseases. InterferenceNot stipulated Calcium, ionized (IcA)Normal1.12 to 1.42 mmol/L (dog); 1.12 to 1.42 mmol/L (cat) CollectWhole blood, 2.0 mL InterpretationResults reflect the concentration of the biologically active, ionized fraction of calcium without the influence of plasma proteins (e.g., albumin). InterferenceThe reported values of iCa can vary with patient's blood pH; iCa decreases as pH increases. Cerebrospinal fluid (CSF)Normal
Patient PreparationGeneral anesthesia is required. Specific training and/or experience is strongly recommended before collection of CSF from the cisterna magna (between the head and C1). Fatalities can result from improper technique. CollectUsually, two 0.5- to 1.0-mL samples are collected in RTTs (no additives).
InterpretationIf one sample contains excessive numbers of neutrophils, the second sample is submitted for culture and sensitivity; treatment recommendations should include use of an antibiotic (preferably intravenous) that will penetrate the blood-brain barrier. InterferenceBlood contamination is the most common interfering factor. An RBC count greater than 30 × 106/L is consistent with peripheral blood contamination. Immediate analysis is recommended. It is not recommended to submit CSF via mail for assessment. ProtocolProper patient preparation and collection technique are critical (see Section 4). Cobalamin (vitamin B12)NormalResults vary considerably among laboratories; consult individual laboratory. Patient PreparationFasted CollectWhole blood, 2.0 mL minimum (RTT) InterpretationTest usually is performed with folate and trypsin-like immunoreactivity (TLI). It is used in the assessment of chronic small bowel diarrhea with associated weight loss. Significantly decreased cobalamin levels support the need to measure TLI (exocrine insufficiency), support a finding of mucosal disease, and may be indicative (in cats) of hepatic disease (hepatic lipidosis). InterferenceHemolysis; lipemia Ethylene Glycol*NormalNegative. “Trace” amounts may be detected in normal patients. CollectUrine (within 3 to 6 hours of ingestion), whole blood, or serum. Collect volume of sample in accordance with manufacturer's directions. SubmitNot applicable. Procedure is an in-hospital test kit for emergency use. InterpretationValues greater than 50 mg/dL indicate exposure to ethylene glycol. Immediate treatment is indicated. Supporting laboratory documentation of ethylene glycol exposure is based on results of serum osmolality (increased), demonstration of an osmolar gap, and anion gap (increased). Blood gas analysis may reveal severe metabolic acidosis. In addition, examination of urine under polarizing light microscopy may detect calcium oxalate crystals if performed within 3 to 6 hours after ingestion. InterferenceSome drugs (pentobarbital and diazepam) will cause false elevations of ethylene glycol in the test kit results but will not induce calcium oxalate crystalluria. ProtocolFollow manufacturer's recommendations for use of the test kit. Fecal fat, 72-hour quantitative collectionNo one wants to either collect or analyze a pound of feces. Better tests are available. See the discussion of TLI in this section. Fecal occult bloodNormalNegative for blood (dog and cat) Patient PreparationDiscontinue all red meat and orally administered drugs at least 3 days before collection of the sample for analysis (see Interference). CollectAbout 1 g of fresh feces SubmitOne gram of fresh feces is sufficient. Sample may be stored for up to 4 days at 2° to 8° C. InterpretationGuaiac test methodology is used to detect the presence of occult blood. Animals with two positive consecutive test results 48 hours apart are likely to have a primary lesion in the GI tract. Benign ulcerative lesion and neoplasia are the two principal rule-outs. InterferenceThrombocytopenia; known platelet disorder; recent aspirin administration; corticosteroid therapy (oral or parenteral); oral iron supplementation; diet containing red meat. FolateNormalResults vary considerably among laboratories; consult individual laboratory. Patient PreparationOvernight fast CollectWhole blood, 4.0 mL (RTT); separate serum from cells immediately. InterpretationTest usually is performed in conjunction with TLI and serum cobalamin (vitamin B12). Decreased levels of folate support the diagnosis of small intestinal mucosal disease. Increased levels of folate support exocrine pancreatic insufficiency and/or small intestinal bacterial overgrowth. InterferenceHemolysis; lipemia FructosamineNormal225 to 375 μmol/L (dog and cat) Consult individual laboratory because test results may vary. CollectWhole blood, 2.0 mL (RTT) SubmitSerum, 1.0 mL; sample must be frozen and shipped on cold packs for overnight delivery. InterpretationThis is a single-sample test representing mean blood glucose over the prior 1 to 3 weeks. Increased fructosamine indicates poor glycemic control (hyperglycemia); declining fructosamine indicates improved or adequate glycemic control. Values greater than 500 µmol/L suggest inadequate glycemic control over the previous 1 to 3 weeks. Values less than the lowest reference range value suggest that the patient sustained significant periods of hypoglycemia over the previous 1 to 3 weeks. Values less than 400 µmol/L and clinical signs of polyuria and polydipsia (PU/PD) and polyphagia are suggestive of a Somogyi phenomenon. Fructosamine levels should not be used to make specific adjustments in daily insulin therapy. InterferenceThe assay is a colorimetric procedure; therefore, significant hemolysis or icterus could affect results. Hypoproteinemia and/or hypoalbuminemia will cause falsely low values. Hyperlipidemia and azotemia may also alter results similarly. Glycosylated hemoglobin (glycated hemoglobin; gly hb)Normal1.7% to 4.9% (dog and cat) Consult individual laboratory because test results may vary. CollectWhole blood, 2.0 mL in EDTA (purple-topped tube) SubmitPlasma, 1.0 mL; separate plasma and refrigerate until assayed. InterpretationThis is a single-sample test representing mean blood glucose over the lifespan of RBCs (approximately 3 to 4 months). This test is used less in veterinary medicine than the fructosamine assay. In dogs, values consistently ranging from 4% to 6% are associated with adequate glycemic control and owner satisfaction. InterferenceStorage at room temperature and for longer than 7 days will decrease values; patients with Hct less than 35% may have lower than expected values. Note: Laboratories must use an assay that has been validated for dogs and for cats. Human assays performed on animal plasma may not be valid. IronNormalConsult individual laboratory because test results may vary. CollectWhole blood, 2.0 mL (RTT) InterpretationResults should be interpreted with total iron-binding capacity (TIBC) and ferritin. Decreased values reflect chronic, not acute, blood loss (e.g., hookworms, intestinal ulceration, bleeding from neoplasia). In cases of iron deficiency, expect TIBC to be normal or high, whereas serum ferritin will be low. Patients with anemia associated with chronic inflammatory disease are expected to have normal to low TIBC, whereas serum ferritin will be normal to high. InterferenceHemolysis; lipemia Lactic acid (lactate)Normal2 to 13 mg/dL (0.22 to 1.44 mmol/L) (dog); results not reported for cats Patient PreparationAvoid venous stasis when collecting sample. Clean venipuncture and rapid draw of sample are important. CollectWhole blood, 2.0 mL, in lithium heparin plasma or in iodoacetate tubes. Some laboratories will accept samples collected in fluoride tubes. SubmitPlasma, which should be rapidly separated from blood. If this is not possible, the sample may be refrigerated immediately at 4° C, but only for 2 hours, at which time the plasma must be separated from blood. InterpretationResting values greater than 6.0 mmol/L indicate severe acidosis and a poor prognosis. Test is also used to assess metabolic myopathies, especially in Labrador Retrievers. InterferenceAspirin, phenobarbital, and epinephrine may alter lactate values. Also, allowing the sample to sit at room temperature will result in an increased level of lactate. ProtocolTo diagnose metabolic myopathy in Labrador Retrievers, two samples are recommended. The first blood sample is collected at rest. A second sample is collected after 10 to 15 minutes of brisk walking or running. Lead, bloodNormalResults vary considerably among laboratories; consult individual laboratory. Usually, values of less than 0.05 ppm in whole blood (or less than 3 ppm in liver or kidney) are within the range of normal. CollectWhole blood, 2.0 mL, in EDTA (lavender-topped tube) or heparin InterpretationRefer to the individual laboratory for specific interpretation of the values reported. Values greater than 0.3 ppm suggest exposure. Values greater than 0.4 ppm are generally considered diagnostic of toxicosis. InterferenceIncorrect tube used for collection or storage of whole blood Lipoprotein electrophoresisNormalNormal values have not been established for the dog and cat Patient Preparation12-hour fast CollectWhole blood, 1.0 mL (RTT) InterpretationTest consists of electrophoretic separation of various lipoprotein categories in serum. It may qualitatively identify various categories of lipoproteins, including chylomicrons, very-low-density lipoproteins (VLDLs), low-density lipoproteins (LDLs), and high-density lipoproteins (HDLs). Standards have not been established for the dog or cat. InterferenceLipemia is not an interfering factor because electrophoresis will separate various lipid fractions. Magnesium (mg)Normal1.5 to 2.5 mg/dL (dog and cat) CollectWhole blood, 2.0 mL, in RTT InterpretationIncreased Mg may reflect renal failure or insufficiency. Decreased Mg is observed in many GI disorders (malabsorption, pancreatitis, chronic diarrhea), renal disease (glomerulonephritis, diuresis, tubular necrosis), and multiple endocrine diseases, as well as with sepsis, blood transfusion, and parenteral nutrition.
InterferenceMg-containing drugs (oral antacids and laxatives) will falsely elevate test results. Some intravenous fluids contain Mg, which also may falsely elevate test results. Falsely decreased values may result from diuretic therapy or intravenous fluid therapy–induced diuresis. Osmolality, estimated (serum)Normal290 to 310 mOsm/kg (dog); 308 to 335 mOsm/kg (cat) CollectWhole venous blood, 2.0 mL, in an RTT or SST InterpretationOsmolality of extracellular fluid (ECF) is determined predominantly by electrolytes, especially sodium, and small molecules (glucose and urea) and is reflective of fluid shifts between the vascular space and the interstitium. Increased ECF osmolality (>350 mOsm/L), or hyperosmolality, is likely to be associated with clinical signs (especially neurologic) because of the shift of water from the interstitial space into the vascular space. Note: Direct laboratory measurement of serum osmolality can be performed but is expensive. Serum osmolality is usually calculated according to the following formula: mOsm/kg=1.86(Na++K+)+(glucose÷18)+(BUN÷2.8)+9 Pancreatic lipase (pl; formerly pli) (also canine: cpl and feline: fpl)Normal2.2 to 102.1 mcg/L (dog—cPL); 2.0 to 6.8 mcg/L (cat—fPL) Patient PreparationFasted for 12 hours before collection of blood CollectWhole blood, 3.0 mL minimum in RTT or SST SubmitSerum, 1.0 mL minimum. Immediately separate serum from clot. Ship serum only. Do not ship whole blood. InterpretationPL is species specific; samples must be labeled “DOG” (cPL) or “CAT” (fPL). Elevated values are considered to be highly specific for a diagnosis of pancreatitis in both the cat and the dog. InterferenceAnticoagulant, hemolysis; moderate or greater lipemia ProtocolSerum should be separated immediately after clot formation and retraction Protein electrophoresis (serum)Normal
Patient PreparationFasted for 12 hours (overnight) to prevent postprandial lipemia CollectWhole blood, 2.0 mL (RTT) SubmitSerum, 1.0 mL. Most laboratories will accept a volume of serum from 0.5 to 1.0 mL. InterpretationMultiple interpretations are possible, depending on the patient's condition. Test usually is performed to assess degree of loss of albumin or increases in one or more globulin fractions (e.g., hypergammaglobulinemia associated with feline infectious peritonitis (FIP), canine ehrlichiosis, multiple myeloma). The test is not used to confirm a diagnosis. Most clinical assessments are made from the shape of the curve in a densitometer tracing of the electrophoresis rather than specific numbers. When requesting serum protein electrophoresis, it is important to request a copy of the curve as well as the quantitated results for each protein fraction. InterferenceLipemia; hemolysis Trypsin-like immunoreactivity, canine (canine tli)Patient PreparationFasted CollectWhole blood, 2.0 mL in RTT SubmitSerum, 1.0 mL. Separate serum from clot. Ship serum only. Do not ship whole blood. InterpretationTLI is species specific; samples must be labeled “DOG.” It is a sensitive and specific test for the diagnosis of exocrine pancreatic insufficiency in dogs and cats. Values less than 2.5 mcg/L, in the presence of clinical signs, support the diagnosis. Values greater than 50 mcg/L have been used to diagnose pancreatitis in dogs. However, TLI has been replaced by the canine pancreatic lipase immunoreactivity (cPLI) assay to diagnose pancreatitis in dogs. InterferenceHemolysis; moderate or greater lipemia Trypsin-like immunoreactivity, feline (feline tli)Patient PreparationFasted CollectWhole blood, 2.0 mL (RTT) SubmitSerum, 1.0 mL. Separate serum from clot. Ship serum only. Do not ship whole blood. InterpretationTLI is species specific; samples must be labeled “CAT.” This is a sensitive and specific test for the diagnosis of exocrine pancreatic insufficiency in dogs and cats. Values less than 2.5 mcg/L in the presence of clinical signs support the diagnosis. Values greater than 100 mcg/L have been used to diagnose pancreatitis in cats. However, TLI has been replaced by the feline pancreatic lipase immunoreactivity (fPLI) assay to diagnose pancreatitis in cats. InterferenceHemolysis; moderate or greater lipemia Serum for PLI and TLI assays may be submitted to the Gastrointestinal Laboratory Department of Small Animal Medicine and Surgery, Texas A&M University, 4474 TAMU, College Station, TX 77843-4474. Hemostasis and coagulationTests of hemostasis are directed at determining platelet numbers and function, activation and abnormalities of the intrinsic and extrinsic clotting cascade, and quantitation of breakdown products of thrombosis and fibrinolysis. Obtain blood samples for evaluation of coagulation abnormalities by careful venipuncture, and insert samples into plastic or silicone-coated glass syringes. Because tissue thromboplastin can activate the clotting cascade, some authors advocate using two syringes and two needles to obtain blood for coagulation tests. First, carefully insert the needle into the vein and withdraw 1 mL of blood. Leave the needle in the vessel, and remove the first syringe. Attach a second syringe and obtain the appropriate volume of blood; then remove the needle from the vessel. Rapidly replace the needle on the second syringe with a fresh needle and then inject the blood sample into the appropriate tubes for later analyses. Platelet tests should be performed on fresh samples within 2 hours of collection. Plasma samples can be spun down and frozen at - 20° C for several days, and at - 40° C for several months to a year for later analyses. Initial in-office screening testsThe initial in-office screening tests for coagulation defects include Hct, peripheral blood smear, activated coagulation test (activated clotting time [ACT]) or activated partial thromboplastin time (APTT), prothrombin time (PT), and, if indicated, buccal mucosal bleeding time (BMBT) assay. HematocritThe patient's Hct and total protein should be evaluated to determine whether anemia is present. The color of the plasma in the spun-down microhematocrit tube can aid in making a diagnosis if intravascular hemolysis (red) or icterus (yellow) is present. The buffy coat from a microhematocrit tube can be evaluated microscopically for the presence of microfilaria in heartworm disease or mast cells in systemic mastocytosis. Peripheral Blood SmearThe peripheral blood smear should be evaluated for RBC morphology, RBC fragments (schizocytes), platelet count, large platelets, WBC count and morphology, and blood parasites. Platelet CountOne of the most simple cage-side tests when determining the cause of a coagulopathy is the platelet count. To perform this test:
Hemorrhage secondary to thrombocytopenia occurs when platelet numbers decrease to less than 40,000/uL (less than three platelets per high-power field). If there are signs of superficial hemorrhage and more than five platelets per high-power field, a thrombocytopathia (platelet function problem) such as von Willebrand disease, disseminated intravascular coagulation (DIC), or aspirin-induced coagulopathy may be present. Activated Coagulation (Clotting) Time (ACT)ACT is a measure of the function of the intrinsic and common coagulation pathway (factors II, V, VIII, IX, X, XI, and XII). The ACT can be used reliably to screen for disorders of secondary hemostasis. Severe thrombocytopenia (<10,000 to 20,000 platelets/µL) and decreased fibrinogen, in addition to decreases in activated clotting factors listed previously, can cause prolongation in the ACT. An ACT tube contains diatomaceous earth that stimulates blood clotting on contact. To measure the ACT:
Normal ACT is 90 to 120 seconds for dogs and 80 to 100 seconds for cats. APTT is another, more sensitive test to detect defects in the intrinsic clotting cascade. It is more sensitive than the ACT in that it will become prolonged earlier than the ACT. Point-of-care coagulation analyzers (SCA-2000, Symbiotics, San Diego, California) are available that require less blood than an ACT and therefore may be the preferred test. Prothrombin Time (PT)PT is a test to determine abnormalities in the extrinsic (factor VII) coagulation pathway. Because factor VII is the most labile clotting factor and has the shortest half-life, PT will become prolonged before any changes in ACT or APTT (intrinsic pathway) occur. The prothrombin-complex clotting factors are II, VII, and X; these factors interact with factor V and fibrinogen in the presence of tissue thromboplastin and calcium chloride. Buccal Mucosal Bleeding Time (BMBT)The BMBT is the time required for platelets to become activated and interact with damaged vascular endothelium to form a primary platelet plug. It is a test of primary hemostasis. The BMBT becomes prolonged with thrombocytopenia (<100,000/μL) and platelet dysfunction syndromes such as von Willebrand disease. The BMBT is usually performed without any sedation in dogs and with ketamine in cats. To measure the BMBT:
If the BMBT is prolonged, von Willebrand disease, nonsteroidal antiinflammatory drug (NSAID) influence, congenital thrombopathies (Bassett Hounds and Otterhounds), and systemic illness (azotemia, hepatic failure, malignancy) should be ruled out. If the BMBT is normal in the face of a normal platelet count and clinical bleeding, tests of the coagulation cascade (APTT, PT, ACT) should be considered. Ancillary tests of hemostasisThrombin TimeThe thrombin time is a measure of the amount of functional fibrinogen in plasma. The test is used in the diagnosis of DIC when fibrinogen levels are low. Fibrinogen levels may also be normal in DIC, but thrombin time will still be altered because of in vivo fibrinolysis. This test is now rarely used, because more sensitive and specific tests such as D-dimer concentration are available for the diagnosis of DIC. FibrinogenFibrinogen levels are used in the detection of DIC. In DIC, fibrinogen levels can decrease as a result of the activation of thrombin and fibrin formation and the activation of plasmin, which causes degradation of fibrin and fibrinogen. Fibrinogen levels can be decreased, normal, or increased in cases of chronic DIC owing to compensatory overproduction. Because of the variability in fibrinogen levels, this test alone is not conclusive to make a diagnosis of DIC. Fibrin(ogen) Degradation Products (FDPs)Fibrin(ogen) degradation products (FDPs; also called fibrin split products [FSPs]) are formed when the enzyme plasmin acts on fibrin monomers, cross-linked fibrin, and fibrinogen. Because fibrinogen can increase during periods of inflammation without DIC, the presence of FDPs alone does not allow a diagnosis of DIC. FDPs are cleared by the hepatic reticuloendothelial system. In cases of hepatic insufficiency or hepatic failure, FDPs can be elevated without concurrent DIC. D-DimersD-dimers are used in the diagnosis of DIC. D-dimers are released as a result of the breakdown of cross-linked fibrin by plasmin. Because D-dimers occur as a result of a stable fibrin clot, elevated levels are more sensitive and specific for a diagnosis of DIC. The PIVKA TestThe PIVKA (proteins induced by vitamin K absence or antagonism) test is most useful in diagnosing vitamin K deficiencies. Moderate deficiencies in Vitamin K–dependent coagulation factors (II, VII, IX, and X) will cause abnormal PIVKA test results. The PIVKA test result becomes prolonged 12 to 24 hours after the PT becomes prolonged. Saline AgglutinationThe saline agglutination test is simple to perform in house and aids in the diagnosis of immune-mediated hemolytic anemia (IMHA). To perform a saline agglutination test:
If the “agglutination” disperses, it is likely caused by rouleaux secondary to inflammation. If the agglutination remains, autoagglutination of RBCs is occurring owing to interaction with antibodies directed against glycoprotein moieties on the surface of the RBC membranes. Note: Management of patients with a confirmed coagulopathy involves correcting any underlying cause, replenishing oxygen-carrying capacity in the form of RBCs or purified hemoglobin, replacing clotting factors and antithrombin in the form of fresh frozen plasma, and maintaining end-organ perfusion. The management of specific conditions and coagulopathies is listed under their subheadings. A more thorough approach to transfusion management is described in Section 1. Submission of samples for coagulation testing
Activated coagulation (or clotting) time (act)Normal90 to 120 seconds (dog); 80 to 100 seconds (cat) Patient PreparationDirect penetration of the vein is important. CollectVenous blood in an ACT Vacutainer tube. Fill to maximum allowed by vacuum. SubmitBlood sample in collection tube per protocol InterpretationACT is a convenient in-hospital screening test that evaluates both the intrinsic and common coagulation pathways. Prolonged clotting time implies coagulation factor deficiency. A specific coagulation factor deficiency must be less than 5% to increase the ACT. Note: hemophiliac patients may have factor VIII or IX activity at only 40% to 60% of normal and yet would have a normal ACT (and a normal APTT). InterferenceThe presence of tissue thromboplastin in sample (e.g., failing to obtain blood from a “clean” venipuncture) will activate the extrinsic pathway. ProtocolA two-tube technique is recommended to eliminate any chance of tissue thromboplastin contaminating the sample. Fill two tubes from the same draw. Use the second tube only. Prewarm the tubes in a water bath or heating block (37° C). Place the filled sample tubes in the water bath or heating block and begin timing. Incubate the sample in the collection tube for 60 seconds for dogs, and 45 seconds for cats. Invert sample every 5 seconds to assess for evidence of clot formation. Stop procedure at first sign of clot formation. Activated partial thromboplastin time (aptt)Normal8.6 to 12.9 seconds (dog); 13.7 to 30.2 seconds (cat) Patient PreparationNone (atraumatic venipuncture is recommended). CollectVenous blood in citrate (BTT); fill Vacutainer tube to the maximum allowed by the vacuum. SubmitCitrated plasma only (plasma must be separated from cells) in RTT. InterpretationAPTT is the most sensitive and specific test of coagulation factor activity. Prolonged APTT implies anticoagulant therapy (heparin) or specific coagulation factor deficiency. InterferenceClotted sample, failure to use citrate as the anticoagulant; incorrect ratio of citrate to whole blood. ProtocolOn collection of blood, invert tube several times to ensure adequate mixing of sample and anticoagulant. Centrifuge immediately. Transfer plasma to RTT and label as “Citrated Plasma.” Blood typing, felineNormalResults reported as positive or negative for blood type A, B, or AB. CollectVenous blood, 1.0 mL, in EDTA (lavender-topped tube) InterpretationThe majority of blood donors should be type A. However, blood typing and cross-matching blood before transfusion in cats is highly recommended, because some type B cats are present in the United States. It has been reported that as little as 1.0 mL of type A blood transfused into a type B cat is fatal. Blood typing for complete dog erythrocyte antigen (DEA)NormalResults are reported as positive or negative for DEA 1.1, DEA 1.2, DEA 3, DEA 4, DEA 5, and DEA 7. CollectVenous blood, 1.0 mL, in EDTA (lavender-topped tube) InterpretationUniversal or A-blood donors should be negative for DEA 1.1, DEA 1.2, and DEA 1.7. Buccal mucosal bleeding time (BMBT)Normal2.6 ± 0.48 minutes (dog); results not reported in cats. SubmitNot applicable. This is an in-hospital screening test for platelet function. InterpretationBMBT is a sensitive and specific test of platelet function. Prolonged BMBT is expected in patients with von Willebrand disease and uremia. Test is not generally recommended for thrombocytopenic patients. InterferenceImproper technique and patients with thrombocytopenia ProtocolThe test entails a standardized cut into the buccal mucosa with subsequent “capture” of blood onto filter paper until bleeding ceases. Clot retraction testNot generally recommended Because of the insensitivity of this test, the clot retraction test is not recommended for the assessment of patients with suspected disorders of hemostasis. Coagulation factor activity (factor assay)The following inherited coagulation factor deficiencies have been reported in dogs and cats:
Other, rare deficiencies have been reported. Diagnosis of Coagulation Factor DeficiencyCoagulation factor deficiency usually is suspected in the individual dog or cat on the basis of initial test results from routine coagulation profiles (see ACT, APTT, and PT in this section). Occasionally it is possible to measure activity of specific factors in individual patients. Specialized laboratories experienced in performing these assays should be consulted regarding sample, sample size, submission requirements, and interpretation. Cross-match: major and minorNormalResults (in dogs and cats) are reported as “compatible” (“no agglutination”) or “incompatible” (“agglutination and/or hemolysis”) in either major or minor cross-match tubes. Collect (Patient)Venous blood, 2 mL, in RTT plus anticoagulated venous blood, 2.0 mL, in lavender-topped tube. Collect (Donor)The same (this is where it's important to label the tubes!). Submit (Patient)Serum, 1 mL, plus anticoagulated whole blood, 1.0 mL InterpretationNo agglutination and/or hemolysis in either tube indicates that the match is compatible and the donor's blood may be used. The presence of agglutination and/or hemolysis in the major cross-match tube indicates that the donor's blood should not be used. The presence of agglutination and/or hemolysis in the minor cross-match tube suggests that the compatibility is not ideal; if another donor cannot be found, the blood can be used—although with caution. The presence of agglutination and/or hemolysis in the donor control (donor cells mixed with donor serum) suggests incompatibility; the donor's blood should not be used. The presence of agglutination and/or hemolysis in the patient control (patient cells mixed with patient serum) likely reflects the patient's diagnosis. Transfusion is indicated. InterferenceIn vitro hemolysis associated with difficulty collecting a sample or inappropriate handling of the blood; profound lipemia (lactescence) Protocol
D-dimer (fragment d-dimer; fibrin degradation fragment)NormalConsult laboratory reference range (dog); studies in cats are lacking. CollectAnticoagulated venous blood, 2 mL, in EDTA or heparin InterpretationD-dimer is the proteolytic fragment of fibrinogen degradation. D-dimer concentration is used in the assessment of DIC in dogs. Elevated levels represent a marker of clot lysis and therefore support a diagnosis of DIC; a negative test result has a high negative predictive value and reliably rules out a diagnosis of DIC. The test also has the potential to identify patients with pulmonary thromboembolic disease, although results are not reliably predictive. InterferenceNone reported Fibrinogen, qualitative (estimated)NormalRefer to laboratory reference range (dog and cat). CollectWhole venous blood, 2.0 mL, in EDTA (lavender-topped tube) InterpretationFibrinogen levels can be estimated as the difference between plasma protein concentrations before and after heating. An increased value correlates with clot lysis and supports the diagnosis of DIC. InterferenceClots in sample ProtocolInvert tube several times to ensure adequate mixing of venous blood and anticoagulant. Fibrinogen, quantitativeNormal100 to 245 mg/dL (dog); 110 to 370 mg/dL (cat) CollectCompletely fill a citrated tube (BTT) with whole blood. Mix thoroughly. Centrifuge immediately. Transfer plasma to an RTT. SubmitPlasma, 1.0 mL, in an RTT; label as “Citrated Plasma.” InterpretationIncreased concentration is associated with DIC. However, there is no single test for the diagnosis of DIC. The clinician must also assess FDPs (increased), APTT (prolonged), PT (prolonged), and platelet count (decreased). InterferenceIncorrect ratio of citrate (anticoagulant) to whole blood; clots in sample; use of anticoagulants other than citrate ProtocolOn collection of blood, invert tube several times to ensure adequate mixing of sample and anticoagulant. Centrifuge immediately. Transfer plasma to an RTT; label as “Citrated Plasma.” Sample is stable for only 24 hours if held at 2° to 8° C; for extended storage, sample must be frozen. Fibrin degradation products (FDPS; fibrin split products [FSPS])Normal<10 mcg/mL (dog); <10 mcg/mL (cat) CollectVenous blood, 2.0 mL, in EDTA or in an RTT Alternatively, sample may be submitted as clotted whole blood placed into a special FDP tube provided by the laboratory (contact the laboratory for additional information). Submit1.0 mL serum or plasma; or, as indicated by the laboratory, clotted whole blood contained in a special FDP tube provided. Sample should be refrigerated. InterpretationAssay is used to document breakdown of fibrin clots. Increased concentration is associated with DIC (see also D-Dimer). However, there is no single test for DIC diagnosis. The clinician must also assess fibrinogen (increased), APTT (prolonged), PT (prolonged), and platelet count (decreased). InterferenceClots in sample, unless sample submitted is clotted whole blood. Pivka test (proteins induced by vitamin k antagonism test; also “thrombotest”)NormalRefer to laboratory reference range (dog and cat). Patient PreparationAtraumatic venipuncture is recommended. CollectCompletely fill a citrated tube (BTT) with whole blood. Mix thoroughly. Centrifuge immediately. Transfer plasma to an RTT. SubmitPlasma, 1.0 mL, in RTT; label as “Citrated Plasma.” InterpretationTest is used in conjunction with PT in the assessment of patients suspected of having warfarin toxicosis. InterferenceIncorrect ratio of citrate (anticoagulant) to whole blood; clots in sample; use of anticoagulants other than citrate ProtocolOn collection of blood, invert tube several times to ensure adequate mixing of sample and anticoagulant. Centrifuge immediately. Transfer plasma to an RTT; label as “Citrated Plasma.” Sample is stable for only 24 hours if held at 2° to 8° C; for extended storage, sample must be frozen. Platelet countNormal166 to 600 × 103/µL (dog); 230 to 680 × 103/µL (cat) Patient PreparationAtraumatic collection is recommended. CollectVenous blood, 1.0 mL, in EDTA (lavender-topped tube) InterpretationDecreased platelet count is indicative of many disorders, including immune-mediated thrombocytopenia (extremely low platelet count), infection, sepsis, and DIC and therefore must be assessed in light of other physical, hematologic, and biochemical parameters. Elevated platelet counts (up to 1 million cells/µL) can be normal for some patients. Cats with extreme thrombocytosis should be tested for feline leukemia virus. InterferenceSlow draw of blood from the vein, transfer of blood from syringe to tube, and traumatic venipuncture may falsely decrease platelet count. Prothrombin time (PT)Normal5.1 to 7.9 seconds (dog); 8.4 to 10.8 seconds (cat) CollectCollect whole blood in a citrated tube (BTT). Fill the tube to the capacity allowed by the vacuum. Invert immediately to mix. Centrifuge immediately and collect plasma. Transfer to a sterile plastic tube, using plastic pipette. Freeze. Note: Label as “Citrated Plasma.” SubmitCitrated plasma, 1.0 mL. Ship sample with dry ice. Store frozen. InterpretationPT is used to assess extrinsic and common coagulation pathways. Prolonged PT is used to assess patients with suspected vitamin K antagonism (warfarin toxicosis). InterferenceIncorrect ratio of citrate to whole blood; clots in specimen; use of a noncitrated anticoagulant (e.g., EDTA in lavender-topped tube). If the citrated plasma sample contacts glass, clotting factor activation may occur. ProtocolOn collection of blood, invert tube several times to ensure adequate mixing of sample and anticoagulant. Centrifuge immediately. Transfer plasma to an RTT. (Label as “Citrated Plasma.”) Sample is stable for only 24 hours if held at 2° to 8° C; for extended storage, sample must be frozen. Von willebrand factor (vWF)NormalResults reported are specific for the laboratory performing the test. CollectCollect whole blood in a citrated tube (BTT). Fill the tube to the capacity allowed by the vacuum. Invert immediately to mix. Centrifuge immediately and collect plasma. Transfer to a sterile plastic tube, using a plastic pipette. Freeze. Label tube as “Citrated Plasma.” Although EDTA (lavender-topped tube) may be accepted by some laboratories, sodium citrated samples are preferred when samples are submitted for vWF testing. SubmitCitrated plasma, 1.0 mL. Ship sample with dry ice. If storing longer than 24 hours, store frozen. InterpretationVon Willebrand disease is the most common inherited hemostatic disorder reported in dogs. This test is usually performed to confirm the diagnosis of von Willebrand disease, in conjunction with the BMBT. Although the condition is inherited, variable degrees of expression are recognized. Dogs with vWF levels ≤30% have a tendency to bleed spontaneously (e.g., epistaxis). InterferenceRecent transfusion may falsely elevate vWF levels. Incorrect ratio of citrate to whole blood, a clotted specimen, and use of a noncitrated anticoagulant (e.g., EDTA in lavender-topped tube) can also affect results. Do not use a glass pipette or glass tube. If the citrated plasma sample contacts glass, clotting factor activation may occur. EndocrinologyAdrenocorticotropic hormone (ACTH), endogenousNormal10 to 70 pg/mL (dog); results not reported for cat. Patient PreparationPatient should be hospitalized overnight. CollectWhole blood, 2.0 mL, in EDTA (chilled, lavender-topped tube). Immediately transfer plasma to plastic tube (ACTH adheres to glass) and freeze. Samples should be stored frozen until assayed. Maximum storage time: 1 month at −20° C. Contact laboratory directly before collecting samples for ACTH testing. Some laboratories request plasma samples be submitted in aprotinin and will provide specially prepared tubes for this purpose. Aprotinin (protease inhibitor) is added to a lavender-topped tube to stabilize ACTH. Freezing the sample is not necessary. The treated plasma should be separated immediately by centrifugation, transferred to a plastic tube, capped, and refrigerated. Transport sample to the lab with cold packs. SubmitPlasma, 1.0 mL; sample should not be allowed to sit at room temperature even for a short period. InterpretationAdrenal tumors and iatrogenic Cushing syndrome are expected to suppress ACTH secretion; pituitary-dependent Cushing syndrome is characterized by excessive plasma concentration of ACTH. InterferenceRecent or current corticosteroid administration; “stress” at or around the time of blood collection. Samples must be handled quickly because ACTH disappears quickly from whole fresh blood. ProtocolAfter overnight hospitalization, the sample is collected between 8 and 9 am the following morning. Acth stimulation test (ACTH “stim”)Normal Cortisol Levels
Note: A level of 17 to 22 mcg/dL is considered “borderline” for dogs; a level of 13 to 16 mcg/dL is considered “borderline” for cats. Patient PreparationNo prior treatment with corticosteroids for at least 5 to 7 days before testing CollectHeparinized whole blood, 2.0 mL (green-topped tube). Do not submit blood collected in EDTA. SubmitPlasma, 0.5 mL minimum for each sample submitted; sample should be refrigerated if shipped. Sample is assayed for cortisol. InterpretationThe test measures endogenous cortisol before and after stimulation with ACTH. This is the most commonly used screening test for hyperadrenocorticism in dogs and cats. Patients with pituitary-dependent hyperadrenocorticism or adrenal tumor are expected to have an exaggerated cortisol response after stimulation with ACTH, assuming that the adrenal glands have retained ACTH responsiveness. Poststimulation values of 22 mcg/dL or greater are considered diagnostic for hyperadrenocorticism in dogs (16 mcg/dL or greater in cats) in the presence of clinical signs (especially PD) and supporting laboratory data and abdominal ultrasound findings. Note: ACTH stimulation does not differentiate between pituitary-dependent hyperadrenocorticism and adrenal tumor. An alternative test to use when screening for canine Cushing syndrome is the low-dose dexamethasone test (see following entry). The ACTH stimulation test is the only reliable test for monitoring patients undergoing o,p′-DDD (Lysodren) treatment of pituitary-dependent hyperadrenocorticism. Dogs with adequate pharmacologic suppression of adrenal function should have unchanged prestimulation and poststimulation values (typically <2.0 mcg/dL for both). InterferenceConcurrent or recent treatment with corticosteroids. Anticonvulsant medications may adversely affect test results. ProtocolSeveral protocols are available; the following are representative.
Aldosterone, serumNormalPretest, 49 pg/mL (mean); posttest, 306 pg/mL (mean); reported range, 146 to 519 pg/mL (dogs). Results not reported for cats. CollectVenous blood, 2.0 mL, in EDTA (lavender-topped tube) as baseline (pretest); and repeat in 1 hour. SubmitPlasma, 1.0 mL, for each of the two samples collected InterpretationLow baseline and minimal or no increase in aldosterone levels support a diagnosis of hypoaldosteronism. The test is designed to distinguish dogs with primary hypoadrenocorticism from those with secondary hypoadrenocorticism. However, the sensitivity of the test in dogs is such that the positive predictive value is relatively low. InterferenceClots in sample ProtocolIn dogs, the pretest and posttest samples are collected at 1-hour intervals after administration of ACTH. Follow the same protocol used to test for hyperadrenocorticism (see ACTH Stimulation Test). Cobalamin (vitamin B12)See also Trypsin-Like Immunoreactivity and Folate. Normal249 to 733 ng/L (dog); 290 to 1500 ng/L (cat) Patient PreparationOvernight fast CollectWhole blood, 4.0 mL (RTT); separate serum from cells immediately InterpretationThe test usually is performed in conjunction with TLI and serum folate. Decreased levels of cobalamin (vitamin B12) support the diagnosis of small intestinal mucosal disease, small intestinal bacterial overgrowth, and exocrine pancreatic insufficiency. There is no significance attached to levels above the reported reference range. InterferenceHemolysis; lipemia Cortisol, resting (basal)See also ACTH Stimulation Test. Normal0.5 to 6.0 mcg/dL (dog); 0.5 to 5.0 mcg/dL (cat) Resting plasma cortisol in dogs is not routinely recommended because of the wide range of values in healthy animals. Although dogs with hyperadrenocorticism are expected to have increased values, reported values may still be within the limits of the reference range listed for normal dogs. Dexamethasone suppression test, low-dose (LDDS test; dexamethasone screening test)Normal Cortisol Levels
Patient PreparationNo treatment with corticosteroids for at least 5 to 7 days before testing CollectHeparinized whole blood, 1.0 mL to 2.0 mL at each collection (green-topped tube). Do not collect blood in EDTA. SubmitPlasma, 0.5 mL minimum for each sample submitted; sample should be refrigerated if shipped. Sample is assayed for cortisol. InterpretationThe test measures endogenous cortisol before and after corticosteroid-induced suppression of cortisol production. This a screening test for hyperadrenocorticism in dogs and cats. Administration of dexamethasone decreases plasma cortisol to less than 1.0 or 1.4 mcg/dL (depending on the laboratory) within 2 to 3 hours in normal dogs. An 8-hr posttest sample showing less than 1.4 mcg/dL is consistent with Cushing syndrome in dogs and cats with clinical signs (especially PD) and supporting laboratory data and abdominal ultrasound findings. Note: LDDS does not differentiate between pituitary-dependent hyperadrenocorticism and adrenal tumor. The 4-hr posttest sample is not interpreted as part of the screening test but is considered an aid in differentiating pituitary-dependent hyperadrenocorticism from adrenal-dependent disease. Demonstrating a transient cortisol suppression (4-hour posttest sample) supports pituitary-dependent disease and rules out adrenal-dependent disease. InterferenceRecent or concurrent corticosteroid administration. Anticonvulsant medications may adversely affect test results. ProtocolCollect pretest sample of plasma; administer dexamethasone (either in sodium phosphate or polyethylene glycol) at 0.01 mg/kg IV in dogs, or 0.1 mg/kg IV in cats; then collect a 4-hr posttest plasma sample, followed by an 8-hr post-test plasma sample. Submit the three plasma samples. (Note the higher dose of dexamethasone used in cats versus dogs.) Dexamethasone suppression test, high-dose (HDDS test)Normal Cortisol Levels
Patient PreparationNo treatment with corticosteroids for at least 5 to 7 days before testing CollectHeparinized whole blood, 1.0 mL to 2.0 mL at each collection (green-topped tube). Do not collect blood in EDTA. SubmitPlasma, 0.5 mL minimum for each sample submitted; sample should be refrigerated if shipped; sample is assayed for cortisol. InterpretationThe test measures endogenous cortisol before and after corticosteroid-induced suppression of cortisol production. The HDDS test is used in dogs with abnormal ACTH stimulation or LDDS test results to distinguish between pituitary-dependent disease and adrenal tumor. Administration of dexamethasone decreases plasma cortisol to less than 1.0 or 1.4 mcg/dL (depending on the laboratory) within 2 to 3 hours in normal dogs. Dogs with an adrenal tumor or pituitary-dependent hyperadrenocorticism are not expected to demonstrate suppression of cortisol after administration of dexamethasone at the dose prescribed. Note: “Suppression” is defined as:
InterferenceRecent or concurrent corticosteroid administration. Anticonvulsant medications may adversely affect test results. ProtocolCollect pretest sample of plasma; administer dexamethasone (either in sodium phosphate or in polyethylene glycol) at 0.1 mg/kg IV in dogs, or 1.0 mg/kg IV in cats; then collect a 4-hour posttest plasma sample, followed by an 8-hour posttest plasma sample. Submit the three plasma samples. (Note the higher dose of dexamethasone used in cats versus dogs.) Estradiol (baseline)NormalNot normally detectable (dog and cat) CollectVenous blood, 2.0 mL, in an RTT InterpretationThis assay is not commonly requested for dogs and cats. Elevated levels have been used to detect testicular tumors and ovarian remnant syndrome. However, better tests are available. InterferenceVariations in results occur with different methodologies used. FolateSee Also Trypsin-Like Immunoreactivity and Cobalamin. Normal6.5 to 11.5 mcg/L (dog); 9.7 to 21.6 mcg/L (cat) Patient PreparationOvernight fast CollectWhole blood, 4.0 mL (RTT); separate serum from cells immediately. InterpretationAssay usually is performed in conjunction with TLI and serum cobalamin. Elevated levels of folate support the diagnosis of small intestinal bacterial overgrowth in the upper small intestine. Values below the reference range support the diagnosis of proximal small intestinal disease. InterferenceHemolysis; lipemia FructosamineNormal225 to 375 μmol/L (dog and cat) Refer to laboratory reference range; ranges vary depending on methodology used. Patient PreparationFasted CollectWhole blood, 2.0 mL, in an RTT (serum), lavender-topped tube (plasma in EDTA) or green-topped tube (plasma in heparin). Caution: Sample must be nonhemolyzed. SubmitSerum or plasma, 1.0 mL InterpretationTest results reflects glycemic levels over the preceding 1 to 3 weeks; test generally is used in assessing quality of glycemic control in patients with diabetes mellitus. InterferenceHemolysis; icterus GastrinNormalVaries according to individual laboratory (dog); results not established for cat. CollectVenous blood, 2.0 mL, in RTT SubmitSerum, 1.0 mL; sample should be kept frozen until assayed. InterpretationTest is not commonly performed. Levels will be elevated in patients with functional gastrinoma, pyloric obstruction, renal failure, and gastric ulcers. There is no significance associated with decreased values. InterferenceConcurrent administration of histamine-2 (H2) antagonist drugs (e.g., cimetidine) Glucagon stimulation, intravenous (IVGS test)Intravenous glucagon stimulation is a complex test protocol to perform and yields results that are not generally reliable in distinguishing patients with type 1 diabetes from those with type 2 diabetes. It has been used to diagnose patients with insulin-secreting tumor. However, risk is associated with performing this test in patients with insulin-secreting tumor. Administration of glucagon will elevate serum glucose, which, in turn, promotes secretion of excessive amounts of insulin; subsequent hypoglycemic crisis is a potential consequence. Glucose curve, 12-hourNormalGlucose concentration ranges between 100 mg/dL and 250 mg/dL for the entire sampling period (dog and cat). Patient PreparationIdeally, a venous catheter should be placed 1 hour before serial collections are started. Patient attitude during testing is important, because stressed or unusually aggressive animals may not be appropriate subjects for this test. CollectVenous blood, approximately 1 mL per collection; plan on drawing as many as seven samples. SubmitSerum from each sample for routine glucose determination InterpretationThis test is used to evaluate glucose levels in diabetic patients receiving insulin, particularly those who may experience recurrence of clinical signs as a result of undertreatment. Objectively, sufficient numbers of samples should be collected to establish a true nadir (lowest point) during the day. For example, if the nadir is greater than 450 mg/dL, each dose of insulin might be increased by 1 to 2 units. When increasing insulin dose, it is appropriate to increase the dose by the same number of units for each administration throughout the day. InterferenceStress. Also, use of portable glucose meters to measure serial glucose levels in individual patients may result in falsely lower values. ProtocolThe patient is given the usual dose of insulin and fed at home in the morning. On arrival at the hospital, a short intravenous catheter is placed in a suitable vein and secured appropriately. Serial samples are collected at 2-hour intervals over a 10- to 12-hour period. At the conclusion of the sampling period, the patient is usually fed and given a second daily dose of insulin, as appropriate. Then you, and the patient, can go home. Glucose tolerance test, intravenous (IVGT test)Not generally recommended NormalBy 60 minutes postinjection, serum insulin should be within 1 standard deviation of the baseline, and serum glucose should be within normal reference range for both dogs and cats. Patient Preparation24-hour fast. Preplacement of an intravenous catheter is recommended. CollectWhole blood, 2.0 mL in an RTT, for each sample submitted SubmitSerum, 1.0 mL, for each sample submitted InterpretationUncommonly performed, the IVGT test is an “insulin secretagogue test” used to distinguish type 1 diabetes from type 2 in cats. (Note: It is appropriate to consider all diabetic dogs as having type 1 [insulin-dependent] diabetes.) Patients with a mean serum insulin level greater than 15 mcg/mL by 60 minutes after injection are likely to have type 2 (non–insulin-dependent) diabetes. However, in cats, results are inconsistent and rarely diagnostic—another reason why this is not a popular test. InterferenceHemolysis. Prolonged contact of serum with RBCs will cause a false decrease in glucose concentration. (Note: Do not use gray-topped tubes to collect samples.) The IVGT test can be adversely influenced by diet, certain drugs (steroids, insulin), stage of estrus, underlying illness or infection (sepsis), and stress. Protocol
Each sample is submitted for both insulin and glucose determination. Glucose tolerance test, oral (OGT test)Not generally recommended The OGT test, although commonly performed in humans, is rarely performed in dogs and cats because of the difficulty associated with reliably administering the required volume of glucose orally. An oral glucose absorption test has previously been described in the literature as a means of assessing patients with malabsorptive GI disorders. Today, considering that superior tests are available, this test is no longer recommended for the assessment of malassimilation in dogs and cats. InsulinNormal5 to 20 μU/mL (dog and cat) Patient PreparationOvernight fast CollectWhole blood, 2.0 mL, in RTT InterpretationTest is indicated for the diagnostic assessment of patients suspected of having an insulin-secreting tumor (e.g., insulinoma). If the patient has profound hypoglycemia at the time the test sample is collected, test results for insulin may be reported as normal. Simultaneous testing of serum glucose is recommended. Low glucose (<60 mg/dL) and an insulin level of greater than 20 μU/mL are consistent with insulin-secreting tumor. InterferenceHemolysis; blood collected in EDTA (plasma) ProtocolMost laboratories recommend that the patient's insulin level be determined in conjunction with blood glucose. Profound hypoglycemia may result in a normal insulin level being reported. A recent meal as well as several drugs can influence insulin concentrations. Parathyroid hormone (PTH)Normal2 to 13 pmol/L (dog and cat). Results vary among laboratories. Patient Preparation12-hour fast CollectWhole blood, 2.0 mL, in RTT. Serum should be separated from cells within 1 hour after collection; serum should be frozen and shipped on ice. Deliver to laboratory via overnight delivery. Keep frozen. SubmitSerum (frozen), 1.0 mL, in sterile plastic tube. Do not ship in an SST. InterpretationPTH levels will be increased in patients with primary hyperparathyroidism, secondary renal or nutritional hyperparathyroidism, and other disorders causing hypocalcemia. No measurable PTH level is consistent with primary hypoparathyroidism. PTH testing should always include iCa assay. InterferenceHemolysis; thawing of sample for extended periods. Parathyroid hormone-related protein (PTHrP)NormalRefer to laboratory reference range values (dog and cat). Patient Preparation12-hour fast CollectWhole blood, 2.0 mL, in RTT. Serum should be separated from cells within 1 hour after collection; serum should be frozen and shipped with ice in plastic tube. Deliver to laboratory via overnight delivery. Keep frozen. SubmitSerum (frozen), 1.0 mL, in sterile plastic tube InterpretationInterpretation of PTHrP entails simultaneous testing for calcium (or iCa) and PTH. PTHrP levels are low to undetectable in patients with primary hyperparathyroidism. Patients with hypercalcemia associated with lymphosarcoma or chronic renal insufficiency will have increased levels of PTHrP. Test InterferenceHemolysis; thawing of sample for extended periods T3 (3,5,3′-triiodothyronine)Normal0.8 to 1.5 mg/dL by radioimmunoassay (RIA) (dog); 0.8 to 1.5 ng/mL by RIA (cat) Results will vary among different laboratories. Patient PreparationNone (patient should not be receiving exogenous thyroid hormone supplementation). CollectWhole blood, 1 to 2 mL, in RTT SubmitSerum, 0.5 mL minimum. Storage and shipment of samples in plastic, rather than glass, containers is recommended. Sample should be frozen and shipped with cold packs. InterpretationT3 is a poor indicator of thyroid function and generally provides little reliable diagnostic information pertaining to thyroid-related disease; baseline T3 does not reliably distinguish between hypothyroid and euthyroid states. Test results for T3 include both free T3 (fT3) and protein-bound T3. RIA is the preferred test method. InterferencePatients receiving exogenous thyroid supplementation can have positive or negative test interference, depending on the dose of drug administered and the time the last dose was given. T3 autoantibody, if present, may falsely lower test results. Note: Storage of serum or plasma in glass can cause a significant false increase in serum T3 concentration. Reverse T3 (RT3; 3,3',5'-triiodothyronine)There are currently no established diagnostic guidelines associated with baseline reverse T3 values in dogs and cats. T3 suppressionNormalSuppression of T4 to 1.5 mcg/dL after seven doses of synthetic T3 (in cats) CollectWhole blood, 3.0 mL, in RTT, for each sample (pretest and posttest) SubmitSerum, 1.0 mL minimum for each sample InterpretationThis test measures T4 and T3 after sequential administration of seven doses of synthetic T3; it may distinguish between euthyroid and slightly hyperthyroid cats. Hyperthyroid cats demonstrate minimal or no decrease in serum T4, which remains at 2.0 mcg/dL or more. T4 values of 1.5 to 2.0 g/dL are nondiagnostic. T3 values should increase in all cats (normal as well as hyperthyroid). If T3 values do not increase, test results are considered invalid. InterferenceHemolysis; lipemia; icterus; blood collected in EDTA ProtocolPretest sample is collected (to be submitted for T3 and T4 testing). Free T4 (fT4)Normal0.8 to 3.5 ng/dL (dog); 1.0 to 4.0 ng/dL (cat) CollectVenous blood, 2.0 mL, in RTT SubmitSerum, 1.0 mL minimum; freeze and store in plastic tubes rather than glass; ship samples with cold packs to arrive for analysis within 5 days of collection. Note: Conventional RIA technology has largely been replaced by the equilibrium dialysis (ED) technology in performing FT4 assays. Recently, IDEXX Laboratories announced the introduction of a new technology for determining FT4 that is faster yet provides results comparable to those achieved with ED technology. InterpretationfT4 is used in preference to conventional T4 to confirm hypothyroidism in dogs and hyperthyroidism in cats. Results less than 0.8 ng/dL (and especially less than 0.5 ng/dL) are consistent with a diagnosis of hypothyroidism in dogs. As with conventional T4 levels, fT4 levels in cats that exceed 4.0 ng/dL are consistent with the diagnosis of hyperthyroidism. InterferenceStoring and shipping serum in glass containers may alter test results; circulating thyroid autoantibody does not interfere with test results. Results determined by RIA alone may be significantly lower than those determined by the ED method. Severe illness may cause low fT4 values in dogs with normal thyroid function (sick, euthyroid). T4 autoantibody does not interfere with the assay for fT4. Total T4, (thyroxine or tetraiodothyronine)Normal1.5 to 3.5 mcg/dL (dog); 1.0 to 4.0 mcg/dL (cat) Note: A point-of-care enzyme-linked immunosorbent assay (ELISA) test kit for in-hospital assessment of T4 is available. However, it is recommended that ELISA test results be confirmed by RIA. Patient PreparationNone (patient should not be receiving exogenous thyroid hormone supplementation). CollectWhole blood, 1 to 2 mL, in RTT SubmitSerum, 0.5 mL minimum. Storage and shipment of samples in plastic, rather than glass, containers is recommended. Sample should be frozen and shipped with cold packs. InterpretationT4 is produced within the thyroid gland, and therefore the total T4 is the preferred test of thyroid function. The test combines measurement of fT4 plus protein-bound T4. Dogs with T4 levels less than 2.0 mcg/dL are likely to have hypothyroidism (if associated clinical signs are present); cats with T4 levels less than 4.0 mcg/dL are likely to have hyperthyroidism. DogsDecreased values suggest hypothyroidism (dogs); however, dogs with underlying illness not related to abnormal thyroid function may still have abnormally decreased T4 concentration (sick, euthyroid). A comprehensive physical examination and laboratory profile are indicated in establishing a diagnosis of hypothyroidism in dogs. CatsIn middle-aged and old cats, hyperthyroidism becomes an important differential diagnosis when T4 levels exceed 4.0 mcg/dL in the presence of clinical signs. Most cases are caused by a functional multinodular adenoma. Less than 5% of cases are associated with thyroid adenocarcinoma. InterferencePatients receiving exogenous thyroid supplementation can have positive or negative test interference, depending on the dose of drug administered and the time the last dose was given. Underlying illness and T4 autoantibody, if present, may falsely lower test results. Note: Storage of serum or plasma in glass can cause a significant false increase in serum T4 concentration. Thyrotropin, canine (thyroid-stimulating hormone [TSH]; baseline TSH)NormalUp to 0.6 ng/mL (dog); values not established for cats. Note: Lower limits of normal (approximately 0.1 ng/mL) for methodologies used are below the sensitivity of the assay. Patient PreparationNone, if patient is not receiving exogenous thyroid hormone supplementation CollectVenous blood, 1 to 2 mL, in RTT SubmitSerum, 0.5 mL minimum Storage and shipment of samples in plastic, rather than in glass, containers is recommended. Sample should be frozen and shipped with cold packs. InterpretationThis is a reasonable test for the assessment of hypothyroidism in dogs; however, TSH fluctuations can produce normal results in 20% to 40% of hypothyroid dogs. TSH should not be interpreted without having same-sample results for T4 or fT4. A low T4 or fT4 and increased TSH in a dog are consistent with the diagnosis of hypothyroidism. Normal T4 or fT4 and TSH effectively rule out hypothyroidism. Clinical signs and a routine laboratory profile must be part of the diagnostic assessment of any patient suspected of having thyroid disease. InterferenceThe same interfering factors that influence T4 assays are likely to affect TSH. TSH or thyroid-stimulating hormone, canineSee Thyrotropin, Canine. Thyrotropin response (TSH response test)Not generally recommended Initially believed to be useful in diagnosing hyperthyroidism, the TSH response test has been shown in subsequent studies to be limited in the ability of abnormal thyroid tissue to respond to stimulation. Other test limitations, including the removal of bovine TSH from the market, have resulted in the current recommendation against its use. ImmunologyAcetylcholine (ach) receptor antibody for myasthenia gravisNormal<0.6 nmol/L (dog); <0.3 nmol/L (cat) Patient PreparationNone. Collect2.0 to 4.0 mL whole blood Submit1.0 to 2.0 mL serum (may be submitted in an SST). Ship with a cold gel pack during summer months. Do not submit whole blood. InterpretationACh receptor antibody levels exceeding the reference range for the laboratory is highly indicative of acquired myasthenia gravis in dogs and cats. Patients with congenital myasthenia gravis are not expected to have elevated levels. Cranial mediastinal masses are common in cats with elevated levels. Note: The ACh receptor antibody test is significantly more sensitive (fewer false negatives) than the “Tensilon test” for diagnosis of myasthenia gravis.
InterferenceSignificant lipemia (lactescence). Another sample should be collected after a significant fasting period. If the patient is still lipemic after a fast, the clinician should attempt to determine the underlying cause, as this could be a risk for acute pancreatitis or other GI disorders. Allergen-specific immunoglobulin e (ige) antibody test (radioallergosorbent test [RAST]; allergy screen)NormalRefer to laboratory for interpretation of results reported. CollectVenous blood, 2.0 mL, in RTT InterpretationThis in vitro assay is used to identify causative allergens in atopic animals. The RAST has also been suggested for evaluation of patients with suspected food-related hypersensitivity. At this time, results are inconclusive. InterferenceConcurrent corticoid therapy Antinuclear antibody (ANA)NormalResults are reported as a titer (ratio); refer to the laboratory reference range (dog and cat). CollectVenous blood, 2.0 mL, in RTT InterpretationThis is an adjunctive (arguably the most important) test in the assessment of patients suspected of having systemic lupus erythematosus (SLE). Results must be interpreted after considering other underlying disorders in the individual patient. Low positive titers will be reported in patients having any of several disorders, including inflammatory disease, neoplasia, and infectious diseases. A high positive titer, in the presence of associated clinical and laboratory findings, supports a diagnosis of SLE. InterferenceConcurrent illness or infection Antiplatelet antibodyNo commercially available test To date, a sensitive and specific test for the diagnosis of immune-mediated thrombocytopenia (IMT) by determination of antiplatelet antibody has not been developed. Generally, extreme thrombocytopenia (<30,000 platelets/mm3) is managed with immunosuppressive doses of corticosteroids on the assumption that the condition is immune mediated. Coombs test (direct coombs test; direct antiglobulin test [DAT])NormalNegative (dog and cat) CollectAnticoagulated venous blood, 1.0 mL, in EDTA (lavender-topped tube) SubmitEntire sample of anticoagulated venous blood InterpretationThe Coombs test detects presence of antibody and/or complement on the surface of RBCs and supports the diagnosis of IMHA. It is generally reported by degree of positivity: + 1 to + 4. Strength of the reaction does not predict severity of the disease or prognosis. A negative test result does not rule out the diagnosis of IMHA. The test is reported to be positive only 60% to 70% of the time. InterferenceConcurrent steroid therapy; severe autoagglutination Rheumatoid factor, canineNormalNegative (dog); values not established for cats CollectVenous blood, 2.0 mL, in RTT InterpretationThis assay detects the presence of circulating autoantibody directed against IgG. It is an adjunctive test used in the diagnostic assessment of patients suspected of having rheumatoid arthritis or SLE. Results are reported as “positive” or “negative.” A positive test result does not confirm a diagnosis of rheumatoid arthritis. Several other immune-mediated disorders, especially if chronic, can cause positive test results. InterferenceOsteoarthritis; fibrositis; polyarteritis nodosa. Infectious disease serology and microbiologyAnaplasma phagocytophilum ANTIBODYCollectVenous blood, 2.0 mL, in RTT InterpretationLimited studies are available about antibody responses to infection with A. phagocytophilum; refer to the laboratory test results for information on interpretation. InterferenceCross-reactivity with Anaplasma platys is expected. Aspergillus species antibody titer (nonavian)Not generally recommended in dogs and cats The high rate of false-positive and false-negative test results (depending on test methodology) limits the value of serology in establishing a diagnosis of aspergillosis in dogs without clinical signs. NormalNegative (dog and cat) CollectVenous blood, 2 to 3 mL, in RTT
SubmitSerum, 1.0 mL minimum InterpretationIt is recommended to concurrently request Penicillium species titer. A positive antibody titer in a dog that is not responsive to empiric antibiotic therapy and with persistent nasal discharge, masseter muscle atrophy, and erosions of the nasal planum is highly suggestive of aspergillosis. InterferenceA positive test result may simply denote exposure. Babesia antibody titer, canineNormalBabesia canis, <80; B. gibsoni, <320 CollectVenous blood, 2 to 3 mL, in RTT SubmitSerum, 1.0 mL minimum InterpretationTiters greater than 80 for Babesia canis or greater than 320 for B. gibsoni are consistent with the diagnosis of infection in patients with corresponding clinical symptoms. InterferenceThere can be considerable cross-reactivity between serologic assays for Babesia canis and B. gibsoni. Negative results in patients suspected of being infected should be followed with a convalescent sample 4 weeks after the initial test. Bartonella species (bartonella henselae titer)CollectVenous blood, 2.0 mL, in RTT InterpretationDifferent test methodologies are used commercially, including immunofluorescent antibody (IFA) assay, ELISA, and Western blot analysis. Although there is cross-reactivity with other Bartonella species, the test is reported to be relatively sensitive and specific for infection in cats. At issue, however, is whether all cats that test positive are, in fact, clinically ill and whether treatment is indicated on the basis of one positive test result. Results on positive cats may be reported as “Serum, + 1 to + 4.” InterferenceNone reported Blastomycosis antibody titerNormalNegative (dog and cat) CollectVenous blood, 2.0 mL, in RTT SubmitSerum, 1.0 mL minimum InterpretationA positive serologic test result in a dog with clinical signs consistent with blastomycosis does correlate with infection. Many cats with known blastomycosis infection, however, will have negative serologic results. InterferenceNone reported Blood culture (bacteria)NormalNegative (“no growth”) after 10 or more days of incubation (dog and cat) Patient PreparationIdeally, sample should be collected while patient is febrile. The peripheral vein must be surgically prepared before venipuncture. Use at least two veins. Do not collect blood via a catheter. CollectVenous blood, 6 to 10 mL, in a syringe (with no anticoagulant added). SubmitTransfer blood directly to a suitable (commercially prepared) vial containing a blood culture medium. Note: Special media designed to remove certain antibiotics are available for patients that are concurrently receiving antibacterial therapy at the time of sample collection. InterpretationThe laboratory will report identification of any growth and minimum inhibitory concentration (MIC) susceptibility test results. InterferenceContaminating bacteria obtained during the collection process. ProtocolSamples from a separate vein, when feasible, should be collected. Generally, three samples are submitted from the same patient, taken at approximately 1-hour blood intervals, collected by venipuncture (syringe and needle) from different sites. Borrelia burgdorferiSee Lyme Borreliosis. Brucella canis antibodyPreliminary Assessment by RSAT or TATRSAT is rapid slide agglutination test; TAT is tube agglutination test. Patient PreparationNone. CollectVenous blood, 2.0 mL, in RTT InterpretationDogs with a negative test result are likely not to be infected. Follow-up testing is recommended for dogs with a negative test result but high likelihood of infection. Dogs with a positive test result should be retested by agar gel immunodiffusion (AGID) (see following entry) to confirm infection. InterferenceBecause of the nature of the screening tests, the frequency of false-positive test results can be high. ProtocolBoth the RSAT and the TAT should be performed with 2-mercaptoethanol (2-ME) to eliminate interference caused by heterologous IgM (responsible for most false-positive reactions). Note: Optional testing by IFA is commercially available. Consider using IFA to compare with the RSAT and TAT. Confirmatory Test by AGID (Agar Gel Immunodiffusion)NormalTiters less than 50 are considered negative (dog). CollectVenous blood, 2.0 mL, in RTT InterpretationTiters greater than 200 are generally consistent with positive results on blood culture. InterferenceNone reported Canine distemper antibodyIn Cerebral Spinal Fluid (IgG or IgM)NormalNegative (refer to laboratory reference range). Patient PreparationFluid should be collected from the cisterna magna; sample is collected with the patient under general anesthesia and an endotracheal tube placed; sterile technique is required. InterpretationThe presence of any titer for canine distemper virus (CDV) antibody (IgG or IgM) in CSF is consistent with infection, provided there is no contamination of the sample with blood or plasma. CSF titers should be assessed in conjunction with serum antibody titer. InterferenceBlood or plasma contamination of sample during collection may cause false-positive results in vaccinated dogs. Vaccine-induced antibody is not expected to cross into CSF. Note: When individual patients are being assessed for distemper antibody, various laboratory methods are used to perform serology. The virus neutralization (VN) test method for CDV antibody is recommended.
In Serum (IgG or IgM)NormalAny patient with a “positive” titer is considered to have protective immunity. Titer results do not distinguish prior exposure and recovery from vaccination. Uninfected dogs have no evidence of a rising titer when results of the acute and convalescent titers are compared. A single IgM titer is expected to be negative in patients that have a “positive” titer subsequent to vaccination. Vaccination will affect results. Methodology (e.g., VN, IFA) will affect values reported. Refer to laboratory reference range. CollectWhole blood, 2.0 mL InterpretationActual test results may vary from one laboratory to another. Individual laboratories will provide interpretation information. Coccidioidomycosis antibody titerNormalNegative (dog and cat) CollectWhole blood, 2.0 mL, in RTT InterpretationRecent advances in testing have resulted in the use of various test methods by different laboratories. Although AGID has been largely used, latex agglutination and ELISA test methodologies are also available. In cats, serotesting is more likely to be performed for tube precipitin (TP, which is predominantly IgM) and complement fixation (CF, which is predominantly IgG) antibodies. In dogs and cats, false-negative test results can occur. InterferenceCross-reactivity in patients with histoplasmosis or blastomycosis can occur with all test methods used to detect Coccidioides immitis antibody. Cryptococcal antigen (serum or CSF)NormalNegative (dog and cat) CollectVenous blood, 2.0 mL, in RTT; CSF, 0.5 mL SubmitSerum, 1.0 mL; CSF, 0.5 mL InterpretationAny titer to Cryptococcus neoformans is consistent with infection and justifies treatment. Antibody titers for cryptococcosis are not valid. InterferenceNone reported Ehrlichia canis antibodyNormalRefer to laboratory reference range (dog and cat). Results of a point-of-care test for in-hospital use in dogs will be negative in the nonexposed patient. CollectVenous blood, 2.0 mL, in RTT InterpretationInterpretation varies among laboratories and methodologies used to detect antibody. The clinician must consider test results with clinical signs and results of routine laboratory profiles when making the decision to treat a patient with a positive titer. Dogs with confirmed infections may continue to have a positive antibody titer for E. canis for several months after recovery and despite several weeks of antibiotic therapy. Note: Correlation between antibody titer and active infection is poor with all available antibody tests on the market today. InterferenceNone reported Feline coronavirus antibody (FeCoV Ab)Inappropriately called the “FIP Ab test”; not generally recommended Coronavirus titer is not a diagnostic test for FIP. In fact, at this time there is no diagnostic test for FIP. The only value in submitting serum for a coronavirus titer is to identify cats that have a truly negative antibody titer (titered to zero). A negative antibody titer, although exceptionally rare in domestic cats, may denote no prior exposure to coronavirus (FIP).
Ehrlichia species (by PCR)NormalNegative (dog and cat) CollectVenous blood, 2.0 mL, in EDTA (lavender-topped tube) InterpretationReported as positive or negative; positive samples should be subjected to further testing in order to confirm infection. InterferencePCR tests are subject to false-positive results because of minute traces of cross-reacting DNA in the sample. Feline infectious anemiaSee Haemobartonella. Feline coronavirus (by RT-PCR)NormalNegative for coronavirus RNA CollectRT-PCR can be performed on body fluids (including blood, serum, and plasma), frozen tissue, tissue imbedded in paraffin (for histopathology), tissue aspirates, CSF, and feces. Pleural and/or abdominal fluids are preferred. SubmitSpecimens should be submitted in a sterile tube or RTT. Whole blood specimens should be submitted as anticoagulated blood collected in EDTA (lavender-topped tube). InterpretationRT-PCR does not distinguish between benign FeCoV and the coronavirus known to cause FIP; therefore false-positive test results are possible. Results must be correlated with laboratory and clinical findings. The presence of FeCoV in abdominal or pleural effusions correlates well with active infection. InterferenceNot reported. Feline coronavirus antibody (FeCoV Ab)Inappropriately called the “FIP Ab test”; not generally recommended as a valid diagnostic test for cats suspected of having FIP The presence of FeCoV antibody, regardless of level, is not diagnostic for FIP. The only value in submitting serum for a coronavirus titer is to identify cats that have a truly negative antibody titer (titered to zero) and therefore have not been exposed to FeCoV. A negative antibody titer, although uncommon among domestic cats, may denote no prior exposure to coronavirus (FIP). Feline leukemia virus antigen (FeLV Ag; P27 ag test)All commercial and in-hospital FeLV tests detect antigen, not antibody. NormalNegative (denotes absence of virus) CollectIFAWhole blood, 1.0 mL, in EDTA (lavender-topped tube) ELISAWhole blood, 2.0 mL, in RTT SubmitIFABuffy coat smear or 1.0 mL anticoagulated whole blood collected in EDTA. Note: IFA is the preferred method for assessing bone marrow aspiration samples for FeLV Ag. InterpretationBoth IFA and the ELISA detect the presence of the core protein p27. IFAA positive test result identifies the presence of FeLV cell-associated antigen (in WBCs and/or platelets) and defines “persistent infection,” especially in cats with clinical and/or laboratory signs consistent with FeLV infection. ELISAA positive test result identifies the presence of soluble, circulating FeLV antigen; healthy cats with a positive test result should be retested in 1 to 2 months to reassess virus status or should be subjected to corroborative testing by IFA. NoteThe American Association of Feline Practitioners (AAFP) and the Academy of Feline Medicine (AFM) AAFP/AFM Task Force on Feline Retrovirus Testing stresses that healthy cats with positive test results may have false-positive test results (by either method). Corroborative testing using a different test method is indicated. A positive test result in a cat with clinical signs suggestive of chronic illness, lymphoid neoplasia, or significant hematologic abnormalities is highly indicative of infection. Negative test results are highly accurate. InterferenceFeLV vaccination will not interfere with test results, regardless of test method used. IFAThrombocytopenia and/or leukopenia may cause false-negative test results. Poor slide quality, eosinophilia, and hemolysis may influence ability to accurately read stained slides. NoteThe 2008 AAFP Feline Retrovirus Management Guidelines make no stipulation that the IFA for FeLV Ag is the “confirmatory test” for cats with positive ELISA results. In fact, ELISA is more sensitive than IFA in detecting the presence of FeLV antigen. Feline immunodeficiency virus antibody (FIV ab)NormalNegative (negative test results indicate no prior FIV exposure). CollectWhole blood, 2.0 mL, in RTT SubmitSerum, 1.0 mL each for IFA (or ELISA) and Western blot analysis InterpretationCats with a positive test result by IFA (or ELISA) should be subjected to confirmatory testing by Western blot analysis. InterferenceAny cat having received at least one inoculation with the FIV vaccine (killed, adjuvanted product) will produce interfering antibody that is detected by all commercially available FIV Ab tests (IFA, ELISA, Western blot analysis). False-positive test results are expected to persist for at least 1 year after vaccination. Currently, there is no test that will reliably and consistently distinguish between infected and vaccinated cats, including PCR. Also, kittens that have nursed from vaccinated queens are expected to have a false-positive test result for FIV antibody associated with maternally derived antibody. Duration of the false-positive results is unknown. Kittens younger than 6 months of age are expected to have maternally derived antibody if the queen is infected and may have a false-positive test result when tested by IFA or ELISA. Subsequent testing of positive kittens at 6 months of age or older is indicated to determine true infection status. Note: The 2008 AAFP Feline Retrovirus Management Guidelines (available at www.catvets.com) stresses that healthy cats with a positive test result (by IFA or ELISA) may have false-positive test results, especially in populations in which the prevalence of infection is low. Confirmatory testing is indicated using the Western blot analysis. Negative test results are highly accurate. Giardia antigenNormalNegative for antigen (dog and cat) Collect2 to 5 g of fresh feces SubmitEntire sample in a sterile container; sample can be stored for 24 hours at 2° to 8° C. Frozen feces may be stored for slightly longer periods. InterpretationTest results are reported as either positive or negative for antigen; positive test results are expected in dogs or cats during active cyst and trophozoite shedding. The zoonotic potential of canine and feline giardiasis is controversial. InterferenceExtended or improper storage of the sample could result in false-negative results. Heartworm antibody, felineSee also Heartworm Antigen, Feline. CollectWhole blood, 1.0 mL, in RTT InterpretationTest results should be interpreted in conjunction with a heartworm antigen test performed on the same sample. Because diagnostic confirmation of heartworm infection in cats is problematic (for several reasons), serologic test results must be considered in light of other laboratory and radiographic assessments. A negative heartworm antibody (HWAb) test result suggests that there has been no exposure to Dirofilaria immitis. A negative result typically is used to rule out feline heartworm infection. A positive HWAb test result only supports prior exposure. It does not confirm infection. Cats that are positive for HWAb should be subsequently tested for heartworm antigen (see later). InterferenceMarked hemolysis or lipemia Heartworm antigen, felineNote: See also Heartworm Antibody, Feline. CollectWhole blood, 2.0 mL, in an RTT InterpretationTest results should be interpreted in conjunction with an HWAb test performed on the same sample. Because diagnostic confirmation of heartworm infection in cats is problematic (for several reasons), serologic test results must be considered in light of other laboratory and radiographic assessments. A negative heartworm antigen (HWAg) test result is not diagnostically useful; heartworm infection is still possible. A positive HWAg test result is highly specific; infection is likely. InterferenceMarked hemolysis may cause a false-positive test result. A cat with only male heartworm infection will not have a positive result. Low worm burdens (common) may result in false-negative test results. Heartworm antigen, canineCollectWhole blood, 2.0 mL, in RTT InterpretationA negative (HWAg) test result implies no infection; a positive HWAg test result strongly supports active infection. InterferenceMarked hemolysis may cause a false-positive test result. A dog with a low worm burden may have a false-negative test result. Note: The canine HWAg test may remain positive for up to 16 weeks after adulticide therapy. Haemobartonella (feline infectious anemia; mycoplasma haemofelis, mycoplasma haemominutum)CollectWhole blood, 1.0 mL in EDTA (lavender-topped tube) SubmitSubmit entire sample InterpretationA positive test result is supportive of the diagnosis of infection; a negative test result implies no exposure. InterferenceSample contamination; improper handing; extended storage times. Samples are stable for 48 hours if refrigerated at 2° to 8° C. Leptospirosis antibody titer by microscopic agglutination test (MAT)CollectWhole blood, 4.0 mL, in RTT InterpretationFor dogs (and cats), laboratories in the United States typically provide titers for at least the following serogroups: Leptospira canicola, Leptospira icterohaemorrhagiae, Leptospira grippotyphosa, Leptospira pomona, Leptospira bratislava, and Leptospira autumnalis. A positive test result may indicate infection (high titers in the presence of clinical signs), prior exposure, or recent vaccination. The serogroup having the highest antibody MAT titer is generally considered to be the infecting serogroup (see Interference). A negative titer indicates no recent exposure or vaccination. Caution: Interpretation of Ab titer results for leptospirosis on the basis of a single serum sample in previously vaccinated dogs is difficult and may not be indicative of infection. A single positive antibody titer for any serovar in a healthy, recently vaccinated dog is not diagnostic for infection. Documentation of a rising titer, based on test results of two samples 3 to 4 weeks apart, is often recommended to confirm a diagnosis. InterferenceRecent vaccination, regardless of the titer and the number of vaccine serovars administered, can result in higher-than-expected titers for multiple serogroups. Cross-reactivity within the MAT can be significant, leading to “positive” titer results for multiple serogroups on the same sample. In dogs with active leptospirosis, the serogroup having the highest MAT titer may not, in fact, be the infecting serogroup. Note: When submitting samples for leptospirosis serology, it is important to provide information regarding date of last vaccination (if known), key clinical signs, and known laboratory abnormalities. Leptospirosis by RT-PCRCollect4 mL fresh urine in a sterile container Submit4 mL urine. Keep refrigerated. Urine specimen should be shipped promptly in a sealed container. Contact the laboratory regarding shipping instructions. InterpretationUrine specimens for PCR for leptospirosis should be submitted at the same time as serum submitted for corresponding MAT. Test results will be interpreted by the laboratory. InterferenceSample contamination and test-related sensitivity or specificity can result in false-positive or false-negative results. Lyme borreliosis (borrelia burgdorferi)Qualitative C6 Antibody by ELISA (SNAP 3Dx or SNAP 4Dx Test)CollectVenous blood, 1.0 mL, in a syringe or RTT (for submission) SubmitUse collected sample for the point-of-care (SNAP) test. Submit a minimum of 0.5 mL of serum if test is being sent to a commercial laboratory. InterpretationA positive test result denotes exposure to B. burgdorferi; the presence of C6 antibody has a high correlation with infection. In dogs, infection is not always associated with clinical signs. The decision to treat or not to treat a healthy dog with a positive test result is based on the clinician's assessment of the individual patient and supporting laboratory data. Occasionally a dog will have a negative test result subsequent to treatment. However, this an inconsistent finding. Use of the quantitative C6 antibody test to monitor response to treatment is recommended. InterferenceNone; prior vaccination (regardless of vaccine used) will not cause false-positive test results. ProtocolSample may be submitted to a commercial laboratory or can be rapidly assessed in the hospital with a point-of care (SNAP) test; follow manufacturer's procedure outline* . Note: PCR testing of blood or serum for Lyme borreliosis is not recommended owing to the ability of spirochetes to reside, undetected, in tissue, resulting in a high number of false-negative test results. Quantitative C6 Antibody Test for Canine Lyme DiseaseNormalUsually less than 30 antibody units (dog); refer to the laboratory reference range. CollectVenous blood, 2.0 mL, in RTT InterpretationPatients with antibody levels greater than 30 antibody units by the quantitative assay may be at risk of developing clinical disease. Patients with an initial positive test result that undergo treatment for Lyme borreliosis infection can be monitored for response (decline in antibody level) to treatment over time. InterferenceNone; prior vaccination (regardless of vaccine used) will not cause false-positive test results. ProtocolThe quantitative test generally is indicated for patients that (1) have tested positive by the SNAP test and/or (2) are undergoing treatment for Lyme borreliosis. Borrelia Burgdorferi Antibody (IFA and Western Blot Analysis)The sensitivity and specificity data on C6 antibody support the recommendation that routine laboratory testing of patients suspected of having Lyme borreliosis be based on either the C6 antibody (SNAP test) or the quantitative C6 antibody test. Indirect Fluorescent Antibody (IFA); Also, Immunofluorescent AntibodyNormalValues vary among laboratories. A negative titer is normal and indicates no exposure to B. burgdorferi or recent vaccination. CollectWhole blood, 2.0 mL, in RTT InterpretationTiters determined by IFA may not distinguish between vaccinated and infected dogs. Lyme borreliosis titers determined by IFA are indicated only in dogs that have not been vaccinated against Lyme disease. Lyme borreliosis vaccination can result in a positive titer. Dogs with a positive test result should be subjected to either the Western blot analysis or the quantitative C6 antibody test (preferred). InterferencePrior vaccination against Lyme disease can result in a positive test result. Western Blot AnalysisNormalResults vary among laboratories. A negative test result is normal and indicates no exposure to B. burgdorferi. CollectWhole blood, 2.0 mL, in RTT InterpretationTiters may distinguish between vaccinated and infected dogs. Western blot analysis is indicated for dogs that have a positive IFA titer, as an alternative test. InterferencePrior vaccination with a whole-cell, killed B. burgdorferi vaccine may complicate interpretation of the Western blot analysis. Parvovirus antibody igg (canine and feline)In Serum (IgG or IgM)NormalAny patient with a “positive” titer is considered to have protective immunity. Titer results do not distinguish prior exposure and recovery from vaccination. Uninfected dogs and cats have no evidence of a rising titer when results of the acute and convalescent titers are compared. Methodology (e.g., hemagglutination inhibition [HI], IFA) will affect actual values reported. Refer to laboratory reference range. CollectWhole blood, 2.0 mL InterpretationActual test results may vary from one laboratory to another. Individual laboratories will provide interpretation information. Rabies titer by favn (fluorescent antibody virus neutralization)Samples may be submitted directly to:
NormalProvided by the Rabies Laboratory. Results determine whether or not a dog or cat has responded to rabies vaccination. Titer results are not generally acceptable by states as an index of immunity and cannot be used in lieu of local or state rabies vaccination requirements. Patient PreparationRabies vaccine should not be administered less than 3 weeks before collection of blood to ensure maximal postvaccination response. Microchip identification number is requested when submitting samples.
CollectVenous blood, 2.0 to 4.0 mL; allow blood to completely clot. SubmitSerum (clear) 1.0 to 2.0 mL. Sample should be sent to the laboratory in a sealed, leakproof tube then placed inside a Ziploc bag. Ship in a padded box with dry ice or gel packs. Important: An “FAVN Report Form,” provided online by the Rabies Laboratory, must accompany the sample. Entries on the form cannot be changed once the form has been submitted; check carefully for errors before shipping. Although overnight shipping is recommended, samples may be refrigerated and stored for up to 7 days. Do not ship to arrive on a weekend or holiday. InterferenceGross hemolysis; lipemia; samples other than serum (e.g., plasma is not acceptable). Other causes for sample to be rejected include insufficient quantity of serum, bacterial contamination of sample, and unlabeled sample. Note: FAVN rabies antibody results for dogs and cats are required by some rabies-free countries and regions before entry. Positive test results may be required before a dog or cat can leave the United States. Antibody titers determined by the RFFIT (see later), which measures rabies virus neutralizing antibody (RVNA), are not acceptable when dogs or cats are being exported. Rabies titer by rffit (rapid fluorescent focus inhibition test for rabies virus neutralizing antibody)NormalRabies antibody titers determined by RFFIT cannot be interpreted as an index of immunity and are not used when exporting animals to rabies-free countries that require testing before exportation. CollectWhole blood, 4.0 mL, in RTT SubmitSerum, 2.0 mL (minimum is 500 µL), in a leakproof container (e.g., with screw-on cap). Place sample container inside a second container with gel packs or dry ice. Overnight shipping is recommended. Note: Values for a “protective titer” in animals have not been established and will not be reported by the laboratory. The presence of RVNA in serum is indicative of an immune response to rabies but does not distinguish between antibody from vaccination and rabies virus exposure. RVNA levels are not to be used in place of current vaccination for either management of rabies exposure or for determination of booster vaccinations for animals. InterferenceGross hemolysis; lipemia; samples other than serum (e.g., plasma is not acceptable). Other causes for sample to be rejected include insufficient quantity of serum, bacterial contamination of sample, and unlabeled sample. Rocky mountain spotted fever (RMSF)NormalNegative (dog and cat) CollectWhole blood, 2.0 mL, in RTT InterpretationGenerally, two samples are recommended (“acute” and “convalescent”), obtained 2 to 3 weeks apart. Titers reported vary among laboratories. The laboratory performing the titer will provide recommendations for interpreting results. Toxoplasmosis titers (IgG AND IgM)NormalSee Interpretation CollectWhole blood, 2.0 mL, in RTT InterpretationA positive titer denotes exposure, not active infection. IgG and IgM titers typically are reported individually. A titer greater than 1:256 for IgM is consistent with active infection in patients with clinical signs (e.g., pneumonia in cats, myositis in dogs). It is recommended that two samples for IgG titer be submitted; samples should be collected 2 to 3 weeks apart. A fourfold or greater rise in titer within 2 to 3 weeks is supportive of the diagnosis of active infection. Cats seropositive on a single titer are unlikely to be shedding oocysts. InterferenceHemolysis; lipemia Vaccine titersSee listing under specific pathogen. Laboratories providing vaccine titers typically limit these services to canine parvovirus, canine distemper, and feline panleukopenia. A limited number of laboratories offer titers for feline herpesvirus-1 and feline calicivirus. Several university and commercial laboratories now provide antibody titers for selected canine and feline viruses as a means of assessing immunity derived from prior vaccination. National laboratory standards for determining serum antibody titers against these pathogens have not been established. Because methods for performing titers vary among laboratories, titer results and ranges also can vary dramatically. It is recommended that samples be analyzed by laboratories using the VN test (for canine distemper) and HI (for canine parvovirus and feline panleukopenia). Note: A “positive” antibody titer usually will equate to “protective immunity.” A “negative” antibody titer does not necessarily equate to “susceptibility.” UrineAn RTT is the preferred collection tube for urinalysis. A Copan swab can be used for urine culture, but this precludes quantitation of bacteria, if present. Urine for culture is best collected by cystocentesis and transported with a cold pack to prevent bacterial overgrowth. Microalbuminuria test (early renal disease [ERD] in-hospital test kit)NormalNegative test strip indication (dog and cat) Collect2-mL (minimum) aliquot of urine in a clean container InterpretationTest strip indicator grades the approximate degree of microalbuminuria. The manufacturer of the test kit provides recommendations for interpreting test results. However, it should be noted that a positive test result in clinically normal dogs is not known to be predictive of impending renal disease. In various studies, it has been shown that a significant percentage of healthy dogs and certain breeds (soft-coated Wheaten Terriers) will have positive test results. Until more information is available about the clinical utility of this test, its use should be restricted to monitoring urine protein loss in patients with known or suspected glomerular disease. InterferenceBlood contamination of urine sample Urine cortisol:creatinine ratio (UC:CR, urinary C:C ratio)NormalVaries according to individual laboratory and test methodology used (dog and cat) Patient PreparationOwner should collect urine at home on the day (morning is preferable) that the test is submitted, thereby reducing stress-induced artifact. Collect3.0- to 5.0-mL aliquot of pooled urine in a sterile container SubmitSame; sample should be refrigerated during transport to the laboratory. InterpretationThe UC:CR is reported to have high sensitivity (negative predictive value) and therefore has been recommended to rule out the diagnosis of hyperadrenocorticism in dogs. Controversy exists regarding the diagnostic value of the UC:CR to diagnose canine Cushing syndrome. Reference values for the cat are not reported. The test currently is not recommended as a single diagnostic test. In serial UC:CR studies performed in hyperthyroid cats, elevated ratios were observed; successful treatment (medical and surgical) did result in a significant decrease in UC:CR in cats. InterferenceThe effect of urine collected from hospitalized dogs (stress) versus urine collected from dogs at home remains an arguable variable. Owners should be advised to collect urine at home on the scheduled day of examination and testing. ProtocolInstruct the owner to collect urine in a single, clean container over 2 consecutive hours on the same day that the urine sample is to be submitted to the laboratory. A 3.0- to 5.0-mL aliquot of pooled urine is submitted for analysis. Note: Not all commercial laboratories offer this test. Check before submitting. Urine protein-creatinine ratio (UP:Cr; P:Cr; UPC)NormalRatio <0.3 (dog); ratio <0.6 (cat) Collect2- to 3-mL aliquot of randomly collected urine in a clean container InterpretationUP:Cr titer greater than 1.0 is consistent with the diagnosis of pathologic proteinuria. The ratio does not confirm the source of the protein loss. However, in patients with consistent hypoalbuminemia and significantly elevated urine P:Cr, loss of protein through the glomerulus is likely (e.g., glomerulonephritis). InterferenceBlood contamination (cystitis, cystocentesis) Footnotes*Vacutainer is the registered trademark of Becton, Dickinson and Company, Franklin Lakes, New Jersey (United States). *Ethylene Glycol Test Kit, PRN Pharmacal, Pensacola, Florida. *IDEXX Laboratories, Westbrook, Maine, United States. Which of the following piece of information found on a specimen label is not optional?Study questions. What is the most important action a phlebotomist can do to prevent the spread of infection?The performance of routine vascular access procedures by skilled phlebotomists requires, at a minimum, the use of gloves to prevent contact with blood. Airborne precautions may be considered to provide a level of safety against infectious diseases such as tuberculosis, influenza, and COVID-19.
Which of the following information is essential for labeling a patient's specimen?The label must contain the following legible information: Patient name. Patient medical record number, with check digit. Patient location.
What is the appropriate action for a phlebotomist to take first after being stuck with a contaminated needle?Flush splashes to the nose, mouth, or skin with water. Irrigate eyes with clean water, saline, or sterile irrigants. Report the incident to your supervisor. Immediately seek medical treatment.
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Which of the following pieces of information is optional for a test requisition on an inpatient?
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