How to Conduct and Interpret Systematic Reviews and Meta-Analyses

Abstract

Systematic reviews with or without meta-analyses serve a key purpose in critically and objectively synthesizing all available evidence regarding a focused clinical question and can inform clinical practice and clinical guidelines. Performing a rigorous systematic review is multi-step process, which includes (a) identifying a well-defined focused clinically relevant question, (b) developing a detailed review protocol with strict inclusion and exclusion criteria, (c) systematic literature search of multiple databases and unpublished data, in consultation with a medical librarian, (d) meticulous study identification and (e) systematic data abstraction, by at least two sets of investigators independently, (f) risk of bias assessment, and (g) thoughtful quantitative synthesis through meta-analysis where relevant. Besides informing guidelines, credible systematic reviews and quality of evidence assessment can help identify key knowledge gaps for future studies.

Figure 1

Differences between traditional meta-analyses and network meta-analyses. In traditional pairwise meta-analysis, only head-to-head direct comparisons can be analyzed. In contrast, network meta-analyses involve the simultaneous analysis of direct evidence (from randomized controlled trials (RCTs) directly comparing treatments of interest, indicated by solid arrows) and indirect evidence (from RCTs comparing treatments of interest with a common comparator, indicated by dotted arrows) to calculate a mixed-effect estimate as the weighted average of the two.