Systematic Review and Evidence Synthesis

Once you have your final set of included articles after the full-text screening, you will extract the data to synthesize. Evidence synthesis projects require a rigorous approach to data extraction. Extraction is usually done by creating a data extraction form. You should pilot test the form with a small subset of the final included articles, to make sure that the team members agree on the fields in the form and that all of the required data is being extracted.

Similarly to the screening process, data from each study should be extracted independently by two different people, who then compare their findings to reach consensus. The extracted data is then synthesized and forms the basis of the final paper. 

Tools to help with data extraction:

• Covidence
• Google Forms (warning: changes made in a Google sheet that your form feeds into will not be maintained if you enter more data into the form)
• Qualtrics
• RedCap
• SRDR
• RevMan

These resources offer additional information and examples of data extraction forms:​

Brown, S. A., Upchurch, S. L., & Acton, G. J. (2003). A framework for developing a coding scheme for meta-analysis. Western Journal of Nursing Research 25 (2), 205–222. https://doi.org/10.1177/0193945902250038

Elamin, M. B., Flynn, D. N., Bassler, D., Briel, M., Alonso-Coello, P., Karanicolas, P. J., … Montori, V. M. (2009). Choice of data extraction tools for systematic reviews depends on resources and review complexity. Journal of Clinical Epidemiology 62 (5), 506–510. https://doi.org/10.1016/j.jclinepi.2008.10.016

Li T., Higgins J. P. T., & Deeks J.J. (editors). Chapter 5: Collecting data. In: Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors). Cochrane Handbook for Systematic Reviews of Interventions version 6.3 (updated February 2022). Cochrane, 2022. Available from www.training.cochrane.org/handbook.