What is the name of the process to determine whether medical care provided to a specific patient?

The basic steps of epidemiologic field investigations that are described in Chapter 3 are adapted here for investigations in healthcare settings.

• Step 1. Verify the diagnosis.
• Step 2. Confirm presence of an HAI outbreak.
• Step 3. Alert key partners about the investigation.
• Step 4. Establish case definition(s).
• Step 5. Identify and count cases.
• Step 6. Organize data according to person, place, time, and size.
• Step 7. Conduct targeted observations, review key concerns with setting healthcare providers, and develop abstraction forms.
• Step 8. Formulate and test hypotheses.
• Step 9. Infection control assessment and implementation of control measures.
• Step 10. Follow-up, communicate findings, and notify patients.

Step 1. Verify the Diagnosis

Early in the investigation, identify as accurately as possible the specific nature of the disease by

• Ensuring that the diagnosis is correct;
• Evaluating for possible laboratory error as the basis for increased diagnoses;
• Evaluating possible changes in surveillance and case definitions; and
• Reviewing clinical findings and microbiological testing results.

Step 2. Confirm Presence of an HAI Outbreak

• An early major step in the investigation is verifying that a suspected outbreak is real. Cases in excess of historical or predicted levels might not necessarily indicate an outbreak.
  • Some cases might be part of an actual outbreak with a common cause, whereas others might be unrelated.
  • Reporting might be increased because of changes in local reporting procedures, changes in the case definition, increased interest reflecting local or national awareness, or improvements or other changes in diagnostic procedures.
• Possible community-associated or other explanations for illness not associated with healthcare should be investigated. Public health surveillance data sometimes can inform investigators about an increase in infections that is initially recognized in healthcare settings but actually is part of a broader community outbreak.
• Pseudo-outbreaks (e.g., those caused by laboratory processing errors or contamination of clinical diagnostic equipment, such as bronchoscopes, without clinical illness) are important to investigate and control because they can lead to unnecessary antibiotic prescriptions, diagnostic procedures, and other potentially harmful interventions to patients. Pseudo-outbreaks also represent opportunities to recognize and correct inadequate infection control processes (e.g., device reprocessing).

Step 3. Alert Key Partners About the Investigation

After confirming an HAI outbreak, investigators should inform key partners.

• Include relevant facility staff (e.g., hospital epidemiologist, infection control practitioner, environmental services department staff, medical staff, administrative leaders, media relations director, and department leads for the affected facility area).
• Ask the clinical laboratory director to save all isolates that might be related to the outbreak.
• Notify local, state, national, and international public health officials, as required.
• Notify regulatory partners (e.g., Food and Drug Administration, Environmental Protection Agency) if the investigation involves regulated medical devices or products.
• Notify professional oversight organizations, as required (e.g., pharmacy boards, clinician licensing boards).

Step 4. Establish Case Definitions

A case definition is used to identify persons who are, or might be, infected and to characterize them in relation to the disease, time and location of exposure or illness onset, and other persons affected. A case definition usually includes

• Clinical information about the disease (e.g., laboratory test results, symptoms, and signs);
• Demographic characteristics of affected patients (e.g., age, race/ethnicity, sex, and occupation);
• Information about the location of possible exposure or time of onset (e.g., what part of an intensive care unit, radiology suite, operating room, ward, or other unit); and
• A defined time during which exposure or onset occurred.

Ideally, the case definition initially should be broad enough to include most if not all cases; it can then be refined as the investigation progresses and more relevant information is accumulated.

The case definition also should be based on the etiologic agent, if known, and can include clinically infected and colonized patients. The specificity of the definition can vary.

• A stratified case definition (e.g., confirmed vs. probable vs. possible [i.e., suspected], or confirmed vs. probable) can be applied to account for the uncertainty of certain diagnoses.
• Confirmed: Usually must have laboratory verification.
• Probable: Usually has typical clinical features and an epidemiologic link to confirmed cases but lacks laboratory confirmation.
• Possible: Usually has fewer of the typical clinical features or weaker epidemiologic links to confirmed cases.

The following are example case definitions:

• A methicillin-resistant Staphylococcus aureus bloodstream infection in a patient in Hospital A’s neonatal intensive care unit during January 1–December 31.
• Isolation of Burkholderia cepacia complex matching the outbreak strain in a hospitalized patient who received Medication A any time during January 1–June 30.
• Fever (temperature >38.5ºC) and compatible symptoms in a patient who had been in an Ebola virus infection–affected country 21 days or less before symptom onset.

Step 5. Identify and Count Cases

Outbreaks often are first recognized and reported by perceptive HCP or identified during surveillance activities. Additional cases related to the outbreak can be identified through multiple types of data and records, for example,

• Central service or supply records,
• Occupational health records,
• Hospital billing records,
• Operative notes,
• Infection control assessment,
• Pathology reports,
• Interviews with physicians,
• Pharmacy reports,
• Log books,
• Purchasing records,
• Medical records,
• Radiology reports,
• Microbiology data, and
• Surveillance records.

Step 6. Organize Data According to Person, Place, Time, and Size

Step 6.1. Create a Line Listing

The line listing, which typically involves using a spreadsheet program so that data can be sorted easily during data analysis, helps guide the outbreak investigation and permits rapid examination of exposures. For each case, collect and array the following types of information encompassed by the case definition:

• Location information. Location within the facility (e.g., room number, bed number, and adjacent rooms).
• Demographic information. Typically, age, sex, race/ethnicity, and occupation, plus other relevant characteristics of the affected population or others at risk.
• Clinical information. Symptoms, signs, and laboratory tests (e.g., culture, serology, or polymerase chain reaction results).
• Risk factor information. Adjust the investigation to the specific disease in question.

Develop a standard questionnaire if patients are to be contacted and interviewed. Box 18.1 summarizes data that should be obtained for a line listing in an HAI investigation.

Example Data to Obtain for a Line Listing

• Patient characteristics (e.g., age, sex, race/ethnicity, comorbidities, birthweight)
• Date of admission
• Date of illness onset
• Date of discharge
• Facility locations/units (i.e., room number, bed, and adjoining room numbers)
• Medications
• Procedures
• Consults (e.g., laboratory or nursing)
• Attending healthcare personnel (e.g., specific nursing staff, respiratory therapists, and physicians)

Collect the information described previously on a standard case-report form, questionnaire, or data abstraction form (Table 18.2).

• Abstract selected key items to build a table. Each column represents a variable, and each row represents a case.
• Add new cases as they are identified. This simple format allows the investigator to scan key information on every case and to update it easily.

An example HAI outbreak abstraction form and user guide are available with the Healthcare-Associated Infection Outbreak Investigation Toolkit (3).

Step 6.2. Construct an Epidemic Curve

Create an epidemic curve (epi curve) to visually demonstrate the outbreak’s magnitude and

time course. The epidemic curve

• Illustrates the course of the epidemic by day, week, or month and can help project its forward trajectory;
• Might help estimate a probable exposure period and, therefore, focus a questionnaire on that period, especially when an approximate incubation period is known or suspected.

• Might enable inferences about the epidemic pattern (e.g., whether common source or person-to-person).

In the example (Figure 18.1), confirmed and probable cases are plotted over time to show the onset of adverse events associated with a contaminated medical product, including markers for key events during the investigation. This example was adapted after a published field investigation (4).

Example line listing for healthcare-associated infection investigations

ICU, intensive care unit; HIV, human immunodeficiency virus.

Fig18-1

Example epidemic curve of patient adverse events associated with a contaminated medical product.

__________
Source: Adapted from Reference 4.

Step 7. Conduct Targeted Observations, Review Key Concerns with Setting Healthcare Providers, and Develop Abstraction Forms

• Healthcare setting investigations often are complex and hypotheses elusive. Most outbreaks are solved through rigorous observation and discussion of procedural concerns with facilities’ HCP.
  • Focus on whether actual practices deviate from recommended infection control practices and the facility’s policies. Such discrepancies are best identified through a combination of direct observations and review of HCP self-reported practices.
  • Examine whether practices differ among HCP.
  • Review recent scientific literature related to the key concerns involved with the outbreak.
  • Observe key activities (e.g., medication preparation, care of vascular access, hand hygiene, adherence to isolation precautions, device and equipment reprocessing, environmental services, and respiratory therapy) related to suspicions about likely transmission pathways that might be involved in the outbreak.
  • In addition to available local and setting-specific tools, use general infection control assessment tools available through CDC to assist with both prevention programs and response scenarios (5).
• Review key concerns with facility HCP to help generate hypotheses about the source and mode(s) of transmission.
  • Are protocols accurate and up-to-date?
  • How does actual practice compare with written or verbal protocols?
  • Are procedures consistently adherent to protocols?
  • Do instances exist where procedures must be performed differently?
  • Have other HCP been observed to perform procedures differently from protocol?
  • What are the challenges with maintaining accurate and consistent techniques?
  • What do you think is the root cause of the outbreak?
  • What procedures or medications might not be documented in the medical record?
  • Is all information in patients’ medical records accurate and current?
• Develop, modify if necessary, and complete abstraction forms. Abstraction forms can include additional details about patients’ illnesses that provide information for analytic studies. Abstraction forms can be adapted from information collected on the line listing to help determine which fields or sections of the abstraction form to include.

Step 8. Formulate and Test Hypotheses

Step 8.1. Conduct Analytic Studies

A case–control study is the approach most commonly used for hypothesis testing for field investigations in healthcare settings. The frequency of exposure to a risk factor among a group of case-patients (i.e., persons with the HAIs) is compared with the frequency of exposure to that risk factor among a group of controls (i.e., persons without the HAIs). Controls must be selected carefully to limit bias; for example, two or more controls for each case-patient might be needed to provide sufficient statistical power. Cohort studies might also be useful in HAIs investigations.

However, analytic studies are labor-intensive and in healthcare settings not always necessary to identify the likely source of an outbreak and to institute control measures. For example, a combination of laboratory evidence and observations of serious lapses in infection control practices that are known to be associated with transmission are frequently sufficient to recommend and implement control measures. The following considerations can influence the decision to conduct an analytic study:

• Will an analytic study add to what is already known about the cause of the outbreak or contribute to the control recommendations?
• Is the necessary technical and statistical support available?
• Is the number of cases large enough to support statistical inferences?
• Can enough controls be selected to minimize bias?
• Is information available for testing possible risk factors?

Step 8.2. Conduct Environmental Sampling and Testing

A major tool available for HAIs investigations is environmental sampling and laboratory analysis. An environmental sampling strategy (i.e., where and what should be cultured) should always be influenced by epidemiologic findings. Molecular methods (e.g., polymerase chain reaction or pulsed-field gel electrophoresis) can be deployed in certain investigations to link environmental samples to clinical specimens. Optimal methods should be discussed with laboratory personnel experienced in environmental sampling to determine how specimens should be obtained and where the cultures can be processed. Often, public health laboratories are needed to support specialized sampling of surfaces, devices, water, or air or when substantial numbers of samples should be obtained. A plan for correctly processing and interpreting results should be established before sample collection. When developing a sampling plan, specify the following:

• Ensure protocols are in place for safe and correct collection and processing of environmental samples. Many environmental pathogens need special procedures for collection, handling, storage, and media for culture growth. Contamination of samples is possible if procedures are inadequate, and overgrowth of organisms in the samples can obscure results for the pathogen of interest. Safety precautions for personnel collecting the samples also need to be followed.
• Use epidemiologic findings to guide testing so that laboratory resources are used appropriately and results can be meaningfully interpreted. Interpretation of results should consider the following:
  • Positive environmental samples are not necessarily evidence of transmission from a particular source; thus, understanding how patients are most likely being exposed to the organism from the environment is crucial. Organisms can be polyclonal even from the same source; for example, biofilms in plumbing systems frequently have many different species and strains of coexisting microorganisms.
  • Conversely, negative environmental samples do not rule out that the pathogen of interest is present or was present at the time of transmission.
  • Samples that test negative must be confirmed to be true-negatives and not inactivated by environmental disinfectants or media preservatives.
  • Laboratory analyses (e.g., pulsed-field gel electrophoresis for DNA fingerprinting) can be used to determine whether environmental isolates match those from patients; however, organisms can be polyclonal.
• Even with correct methods and materials, sensitivity can be low, and negative results do not necessarily rule out environmental reservoirs.

Analytic studies can support a hypothesis even if a source cannot be confirmed by environmental testing.

Step 8.3. Considerations for Testing of HCP

Testing HCP can further support or confirm possible associations between HCP colonization and infection transmission to patients. These scenarios are most readily recognized in point-source outbreaks involving colonized HCP and absence of other clear links among infected patients. Possible transmission from HCP to patients should be considered in the context of the type of organism and investigation into other possible transmission routes.

• HCP testing should only be undertaken after careful consideration of (1) how the results will help control the outbreak, (2) what duty or work restrictions might need to be applied, and (3) a known decolonization or other specific control strategy to undertake for personnel who test positive.
• Testing of HCP provokes anxiety, and positive results can be highly stigmatizing. The rationale for testing should be clearly explained to HCP, and strict discretion should be emphasized when obtaining samples and communicating results.
• Positive results should not necessarily be regarded as evidence of causality because HCP frequently acquire microorganisms from infected patients.
• Because of limitations in the sensitivity of cultures and the potential for transient contamination, negative results can be reassuring in certain scenarios but should not be regarded as excluding the possibility that HCP were involved in transmission.

Step 9. Infection Control Assessment and Implementation of Control Measures

Step 9.1. Infection Control Assessment

Infection Control Domains for Assessment

• Infection control program review
• Infection control training
• Hand hygiene
• Personal protective equipment use, availability, quality, and training
• Prevention of catheter-associated urinary tract infection
• Prevention of central line–associated bloodstream infection
• Prevention of ventilator-associated event
• Injection safety
• Prevention of surgical site infection
• Prevention of Clostridium difficile infection
• Environmental cleaning
• Waste management
• Device reprocessing
• Multidrug-resistant organism surveillance

When investigating an HAI outbreak, an understanding of infection prevention and control is crucial to determine which control measures need to be implemented. A setting-specific infection control assessment tool can help accomplish this task (5,6). Such tools provide a framework for assessing major areas of infection control and help guide a facility infection control assessment. Box 18.2 summarizes major infection control domains to consider when performing an assessment. A physical walkthrough of the specific healthcare setting should be targeted for specific domains, depending on the hypothesized source of transmission (i.e., care locations or others areas hypothesized to be involved in the outbreak), including

• Triage and emergency care departments,
• Inpatient areas,
• Device reprocessing and storage areas,
• On-site or off-site compounding pharmacies,
• Operating or other procedure rooms, or
• Management areas for specific equipment (e.g., hemodialysis machines or ventilators).

Step 9.2. Defining Infection Control Measures

Control measures should be implemented as soon as deficiencies or gaps are identified; these should be aimed at specific links in the infection chain, the agent, the source, or the reservoir. Multiple control measures might be required.

Ultimately, the primary goal is to stop transmission, even when the specific source remains unidentified. Therefore, implementing multiple control measures targeting different possibilities based on the initial observations might be necessary. Table 18.3 provides key examples of immediate control measures that can be used to manage an outbreak.

Certain new or targeted multidrug-resistant organisms warrant consultation with public health departments, and control measures can extend into the community or across healthcare systems. Control measures might include contact tracing, lower thresholds for screening patients and HCP, specialized environmental testing, and implementing systems to adhere to contact precautions or enhanced environmental cleaning and disinfection. A tiered approach for investigating and controlling transmission of such pathogens also might be needed (7).

Step 10. Follow-Up, Communicate Findings, and Notify Patients

Step 10.1. Stages of the Follow-Up Investigation

1. Refining the case definition. Refine the case definition on the basis of data gathered from initial case-patients, controls, and HCP. Capturing all cases and optimizing the power of analytic studies might require narrowing or expansion of the definition.
2. Continuing case finding and surveillance. Continue case finding and surveillance efforts on the basis of the refined case definition. Surveillance should continue, for example, for 1 month, 3 months, or even 1 year (e.g., in a long-term care facility) after the outbreak to ensure it has ended.
3.  Reviewing control measures. Assess adherence and determine whether control measures need to be further enhanced or relaxed.

Immediate control measures for outbreak management

Step 10.2. Communication of Findings

Findings should be communicated to all partners involved in the investigation. This communication typically takes two forms: (1) an oral briefing for local health authorities and (2) a written report (e.g., for CDC or the state or local health department). The final report, which might await laboratory confirmation, should describe (1) the outbreak characteristics, (2) infection control problems that most likely contributed to the outbreak, and (3) any interventions that were instituted and their effects. Additionally, the report should make recommendations for preventing future occurrences (8).

Step 10.3. Patient Notification

Notification of patients potentially exposed to infectious organisms and their healthcare providers should be considered during investigation of HAIs outbreaks, cases involving pathogens of public health concern, or unsafe infection prevention and control practices. Although the circumstances of each outbreak and infection control breach vary, communication needs during notifications are more predictable. CDC has published considerations for when to notify patients and a patient notification toolkit to support HCP and public health personnel throughout the notification process (9).

Depending on the scenario, typical reasons for conducting notifications can include one or more of the following:

• Identify potentially exposed or infected patients who will derive a health benefit through follow-up testing or other clinical evaluation.
• Establish transparency between healthcare providers and patients and other stakeholders.
• Limit the spread of multidrug-resistant organisms or other pathogens of public health concern by identifying exposed patients and their contacts who should be managed under recommended precautions.
• Improve case finding by informing patients and providers about the outbreak and associated exposures and clinical signs and symptoms that might signify the infection of interest.
• Use the notification scenario as an educational and prevention opportunity by reminding healthcare providers about the importance of infection prevention and control.

Examples of recently conducted patient notification scenarios include lapses in injection safety, drug diversion, contact with other patients with drug-resistant organisms, and exposure to contaminated or incorrectly processed devices (e.g., cardiopulmonary bypass heater-cooler units, endoscopes or surgical instruments, and exposure to contaminated medications).

The objectives of patient notifications are to deliver a consistent message quickly to all affected patients and to inform patients about testing or other follow-up actions that should be taken. Major steps include

• Verifying that exposures have occurred and confirming the type of procedure or substances involved;
• Determining the timeframe of the breach and the number of patients potentially exposed;
• Determining the severity of potential risks to patients;
• Determining whether testing or other further evaluation is available or warranted;
• Identifying any options for prophylactic treatment of exposed persons; and
• Determining how and what entity will provide the initial and follow-up care if testing, evaluation, or postexposure prophylaxis are to be offered.

Guidance for assessing unsafe injection practices and other serious infection control breaches includes how to assess whether a breach warrants patient notification and a sample notification letters and other materials (10,11).

Step 10.4. Legal Concerns

HAIs outbreaks can result in litigation and have broad financial and public relations implications for affected facilities. This concern often increases the scrutiny and number of interested stakeholders in the investigation. Pressure might be applied not only to investigate rapidly, but also to implement necessary control strategies quickly. Additionally, public health records of HAIs outbreak responses frequently are the subject of Freedom of Information Act requests. Investigators should keep records of all steps taken, exercise care and discretion in how emails and other communications are used, and assume that any investigation records might become publicly available or used as part of litigation proceedings.

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