SWiM Synthesis without meta-analysis

These methods are rarely documented in systematic reviews, and alternative synthesis approaches are routinely utilized in systematic reviews that lack data suitable for meta-analysis. The lack of transparency in the techniques could bring the review results into question. For example, the Synthesis Without Meta-analysis (SWiM) guideline was created to help guide detailed reporting in intervention reviews that employ alternative synthesis approaches to the meta-analysis of impact estimates. The SWiM guideline for synthesizing quantitative data on intervention effects is described here, as are the nine SWiM reporting elements, together with explanations and examples. 

Summary points 

• Systematic evaluations of health-related treatments frequently employ alternative synthesis methodologies to a meta-analysis of effect estimates, which are referred to as “narrative synthesis.” 
• There are severe flaws in reviews that employ “narrative synthesis,” such as a lack of disclosure of the methodologies used, unclear relationships between the included data, the synthesis, and the findings, and inadequate reporting of the synthesis’s limitations. 
• The Synthesis Without Meta-analysis (SWiM) guideline is a nine-item checklist designed to improve honest reporting for intervention evaluations that employ alternative synthesis methodologies. 
• The SWiM items require users to report on how studies are categorized, the standardized metric used for the synthesis, the synthesis technique, how data are presented, a summary of the synthesis findings, and the synthesis restrictions. 

• The SWiM guideline was created using a best practice method that included significant consultation and formal consensus. 

Synthesis without meta-analysis reporting items 

Item 1: grouping studies for synthesis 

Item 2: describe the standardized metric and transformation method used 

Item 3: describe the synthesis methods 

Item 4: criteria used to prioritize results for summary and synthesis 

Item 5: investigation of heterogeneity in reported effects 

Item 6: certainty of the evidence 

Item 7: data presentation methods 

Item 8: reporting results 

Item 9: limitations of the synthesis 

References 

Campbell, Mhairi, et al. “Synthesis without meta-analysis (SWiM) in systematic reviews: reporting guideline.” bmj 368 (2020).