Using preprints in evidence synthesis: commentary on experience during the COVID-19 pandemic

Key findings: Evidence syntheses are increasingly drawing on preprint servers as a source for emergent literature on COVID-19. Our research group, has conducted a large number of rapid reviews of a broad range of public health topics related to COVID-19. We outline several considerations when including preprints in rapid reviews and lessons learned from this process.

What this adds to what is known?: Including preprints in rapid reviews has implications for the rapid review process and review teams should have clear protocol regarding the selection and coverage of bibliographic databases, indication within reviews where an included study is a preprint and prespecifying any sensitivity analysis (quantitative or narrative) to assess the impact of inclusion of preprints on the overall results and conclusions.

Specific challenges encountered in including preprints in rapid reviews such as those related to matching preprints to subsequent peer review publications and dealing with changes between preprints and peer review publications are presented using three exemplar review, and suggestions for study authors and review teams are provided.

What is the implication and what should change now?: We suggest that preprint study authors include a statement in the final peer-reviewed version of the manuscript with the citation of the preprint version.

Rapid review teams should have a clear policy around whether they will or will not check peer review status of preprints included in a rapid review, and at what point in the review process this would occur.