A Primer on Systematic Reviews and Meta-Analyses.

With the rapid growth of biomedical literature, there is increasing need to make meaningful inferences from a comprehensive and complex body of evidence. Systematic reviews with or without meta-analyses offer an objective and summative approach to synthesize knowledge and critically appraise evidence to inform clinical practice. Systematic reviews also help identify key knowledge gaps for future investigation. In this review, the authors provide a step-by-step approach to conducting a systematic review. These include: (1) formulating a focused and clinically-relevant question; (2) designing a detailed review protocol with explicit inclusion and exclusion criteria; (3) performing a systematic literature search of multiple databases and unpublished data, in consultation with a medical librarian, to identify relevant studies; (4) meticulous data abstraction by at least two sets of investigators independently; (5) assessing risk of bias in individual studies; (6) quantitative synthesis with meta-analysis; and (7) critically and transparently ascertaining quality of evidence.