Data extraction
Once you have your final set of included articles after the full-text screening, you will extract the data to synthesize. Evidence syntheses 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 and 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
For a list of other tools across a range of methodologies:
- SR Toolbox - select the data extraction box on the search screen.
Further reading
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.