Systematic Review and Evidence Synthesis

The final step is to synthesize, map, or describe the data that you have collected in your final manuscript. There are a number of ways in which you can synthesize the results of your included studies.

Resources for meta-analysis and other qualitative and quantitative evidence:

If the studies that you have included are sufficiently similar, one of the ways you can synthesize the data from these studies is via a process called meta-analysis. A meta-analysis is a statistical approach to bring together results from multiple studies.

• Borenstein, M., Hedges, L., Higgins, J., & Rothstein, H. (2021). Introduction to meta-analysis (Second ed.). Hoboken, NJ: John Wiley & Sons. (2009 edition is available online)
• Search for additional books and chapters on conducting meta-analyses

Resources for narrative synthesis:

If your results are more heterogeneous, or different, you would undertake a narrative or descriptive synthesis. The process for this type of synthesis is subjective, and there is no one standardized process.

• Thomson H, Campbell M. “Narrative synthesis” of quantitative effect data in Cochrane reviews: Current issues and ways forward. Cochrane Learning Live Webinar Series 2020 Feb.
  • Part 1 helps navigate some of the confusion over the concepts of "narrative synthesis" or "qualitative review of (quantitative) data" versus the ambiguous use of the terms "narrative review" or "qualitative review"
• Campbell, M., McKenzie, J. E., Sowden, A., Katikireddi, S. V., Brennan, S. E., Ellis, S., Hartmann-Boyce, J., Ryan, R., Shepperd, S., Thomas, J., Welch, V., & Thomson, H. (2020). Synthesis without meta-analysis (SWiM) in systematic reviews: Reporting guideline. BMJ, 368, l6890. doi:10.1136/bmj.l6890