Qualitative Synthesis
Qualitative Synthesis in Systematic Reviews and/or Meta-AnalysesSelecting the best approach for synthesis will depend on your scope, included material, field of research, etc. Therefore, it is important to follow methodological guidance that best matches your scope and field (e.g., a heath-focused review guided by the Cochrane Handbook). It can also be helpful to check out the synthesis and discussion of systematic reviews published by journals to which you plan to submit your review. Show
In almost all cases, a qualitative synthesis of some kind will be part of your systematic review. A quantitative synthesis (e.g., meta-analysis) should only be pursued as appropriate. Meta-synthesis and Qualitative Evidence Synthesis are term sometimes used to describe a systematic review with only a qualitative synthesis. Guidance for Qualitative SynthesisIn some methodological guidance, this stage may effectively be described as a separate methodology altogether. For example, the Cochrane Handbook, Part 2: Core Methods covers synthesis through the lens of conducting a meta-analysis and/or quantitative synthesis. In Part 3: Specific perspectives in reviews, Cochrane goes into more detail about qualitative evidence synthesis in Chapter 21: Qualitative Evidence. Similarly, the JBI Manual for Evidence Synthesis contains a stand-alone chapter, Chapter 2: Systematic Reviews of Qualitative Evidence Considerations and Decisions
Qualitative Synthesis ApproachesThis is not a comprehensive list of approaches. However, it can be a jumping off point for your team as you plan. The selection of approaches listed here is partially informed by Barnett-Page & Thomas (2009) Note: Many of these approaches are also stand-alone qualitative research methods. Content Analysis"In the case of qualitative systematic reviews, raw data consist of qualitative research findings (i.e. text) that have been systematically extracted from existing research reports...The manner in which these findings are coded is largely guided by the research topic and questions and the data that are available for analysis." (Finfgeld-Connett, 2014) Process
Resources for Content Analysis
Thematic Synthesis"Developed out of a need to conduct reviews that addressed questions relating to intervention need, appropriateness, acceptability, [and effectiveness] without compromising on key principles developed in systematic reviews"(Barnett-Paige & Thomas 2009) ProcessAccording to Thomas & Harden (2008):
Resources for Thematic SynthesisThomas J, Harden A. Methods for the thematic synthesis of qualitative research in systematic reviews. BMC Med Res Methodol. 2008 Jul 10;8:45. doi: 10.1186/1471-2288-8-45. PMID: 18616818; PMCID: PMC2478656. Framework SynthesisThe "rationale [behind framework synthesis] is that qualitative research produces large amounts of textual data in the form of transcripts, observational fieldnotes etc. The sheer wealth of information poses a challenge for rigorous analysis. Framework synthesis offers a highly structured approach to organising and analysing data (e.g. indexing using numerical codes, rearranging data into charts etc)." (Barnett-Page & Thomas, 2009) ProcessAccording to Brunton & James (2020):
Resources for Framework Synthesis
Grounded TheoryGrounded theory is defined as "a specific methodology developed by Glaser and Strauss (1967) for the purpose of building theory from data. In this book the term grounded theory is used in a more generic sense to denote theoretical constructs derived from qualitative analysis of data." (Strauss & Corbin, 2008) ProcessAccording to Barnett-Paige & Thomas, 2009, "key methods and assumptions...include":
Resources for Grounded Theory
Meta-EthnographyThis is proposed as an alternative to "Meta-Analysis" (Nolbit & Hare, 1998; Barnett-Paige & Thomas 2009) and "should be interpretive rather than aggregative. We make the case that is should take the form of reciprocal translations of studies into one another" (Nolbit & Hare, 1998) Approaches
Reporting GuidelineeMERGeImproving reporting of meta-ethnography: The eMERGe reporting guidance (documents the development of eMERGe) Resources for Meta-Ethnography
Resources
Meta-Analysis
Meta-analysis“The statistical analysis of a large collection of analysis results from individual studies for the purpose of integrating the findings.” (Glass, 1976) “A statistical analysis which combines the results of several independent studies considered by the analyst to be ‘combinable’.” (Huque, 1988) “Meta-analysis is the statistical combination of results from two or more separate studies.” (Cochrane Handbook for Systematic Reviews of Interventions version 6.3, Chapter 10) The Cochrane Handbook (Chapter 10.1) states:
Choosing to pursue a Meta-AnalysisReasons to pursue a Meta-AnalysisMeta-analyses are a desirable end-goal as a this kind of synthesis can:
Reasons not to pursue a Meta-AnalysisDespite the appeal of the meta-analytic approach, it is vital that studies in the meta-analysis measure the same thing in the same way - that the studies themselves are reasonable to combine statistically. According to Cochrane Chapter 12.1, "Legitimate reasons [for not conducting a meta-analysis] include limited evidence; incompletely reported outcome/effect estimates, or different effect measures used across studies; andbias in the evidence." Table 12.1.a describes scenarios that may preclude meta-analyses, with possible solutions Likewise, a synthesis is only as good as the studies included. In other words, a meta-analysis cannot improve poor quality studies. Considerations and DecisionsThis is not a comprehensive list - as with any analysis, you'll need to select specific approaches based on the kind of data you have.
Resources
Tools for Meta-AnalysesSeveral tools exist for running your own meta-analyses. If you need further support, check out the help tab in this box. Graphical User Interface (no programming required)
Command Line Interface (programming required)
Resources
Present Meta-Analysis ResultsA meta-analysis is most commonly presented as a Forest Plot. Forest PlotIf you are new to the concept of forest plots, check out Dr. Terry Shaneyfelt from UAB School of Medicine How to interpret a forest plot. Alternative Quantitative Synthesis MethodsAccording to Cochrane Chapter 9.5, "There are circumstances under which a meta-analysis is not possible, however, and other statistical synthesis methods might be considered, so as to make best use of the available data." Table 9.5.a from the Cochrane Handbook, represented below, outlines some alternative synthesis method (and one summary method in the first row).
While the Evidence Synthesis Services (ESS) team at the University Libraries is available to support the other stages of a systematic review and/or meta-analysis, we recommend reaching out to the Statistical Applications and Innovations Group (SAIG) for support in the statistical synthesis / meta-analysis. Methodological Guidance
Cochrane Handbook - Part 1: About Cochrane ReviewsChapter III: Reporting the Review (specifically part III.III); Note: if you are not conducting a Cochrane Review, use this resource as a guidepost Cochrane Handbook - Part 2: Core MethodsChapter 9: Summarizing study characteristics and preparing for synthesis
Chapter 10: Analyzing data and undertaking meta-analyses
Chapter 12: Synthesizing and presenting findings using other methods
Chapter 13: Assessing risk of bias due to missing results in a synthesis
Chapter 15: Interpreting results and drawing conclusions
Cochrane Handbook - Part 3: Specific Perspectives in ReviewsChapter 21: Qualitative Evidence
Campbell - MECCIRC59. Addressing risk of bias / study quality in the synthesis (review / final manuscript) C60. Incorporating assessments of risk of bias (review / final manuscript) C61. Combining different scales (review / final manuscript) C62. Ensuring meta-analyses are meaningful (review / final manuscript) C63. Assessing statistical heterogeneity (protocol & review / final manuscript) C64. Addressing missing outcome data (review / final manuscript) C65. Addressing skewed data (review / final manuscript) C66. Addressing studies with more than two groups (protocol & review / final manuscript) C67. Comparing subgroups (protocol & review / final manuscript) C68. Interpreting subgroup analyses (protocol & review / final manuscript) C69. Considering statistical heterogeneity when interpreting the results (review / final manuscript) C70. Addressing non-standard designs (protocol & review / final manuscript) C71. Conducting sensitivity analysis (protocol & review / final manuscript) C72. Interpreting results (review / final manuscript) C73. Investigating reporting biases (review / final manuscript) C77. Formulating implications for practice (review / final manuscript) C78. Avoiding recommendations (review / final manuscript) C79. Formulating implications for research (review / final manuscript) Reporting in Protocol and Final Manuscript
In the Protocol | PRISMA-PData Synthesis (Item 15)Qualitative Synthesis only
Meta-Analysisall of the above plus:
In the Final Manuscript | PRISMASynthesis Methods (Item 13; report in methods)Qualitative Synthesis onlyEssential Items
Additional Items
Meta-Analysis (or other quantitative methods used)all of the above plus: Essential Items
If a random-effects meta-analysis model was used, consider specifying other details about the methods used, such as the method for calculating confidence limits for the heterogeneity variance (Item 13d) Reporting Bias Assessment (Item 14; report in methods)Essential Items
Results of Synthesis (Item 20; report in results)Qualitative Synthesis onlyEssential Items
Meta-Analysis (or other quantitative methods used)all of the above plus: Essential Items
Reporting Biases (Item 21; report in results)Essential Items
Additional Items
Discussion (Item 23)Essential Items
What effect does a metaA meta-synthesis brings together qualitative data to form a new interpretation of the research field. It helps to generate new theories or an explanatory theory of why the intervention works or not.
What is the difference between Metasynthesis and metaIn summary, a meta-analysis is a way of testing a hypothesis whereas a meta-synthesis is a way of developing a new theory. 1) Theory Building – This form of meta-synthesis brings together findings on a theoretical level to build a tentative theory.
What are the advantages of metaThey have been shown to be particularly useful to identify research gaps, to inform the development of primary studies, and to provide evidence for the development, implementation, and evaluation of health interventions (13).
What is the purpose of metaMeta-analyses are conducted to assess the strength of evidence present on a disease and treatment. One aim is to determine whether an effect exists; another aim is to determine whether the effect is positive or negative and, ideally, to obtain a single summary estimate of the effect.
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