Meta-analysis: Everything you wanted to know but were afraid to ask

Abstract

The perceived ability of systematic reviews and meta-analyses to concisely and definitively summarise existing literature regarding a specific medical issue has made them the most highly read and cited form of academic literature. However, the evidence they provide is only as good as the data evaluated and the methodology followed when doing them. In order to conduct a rigorous systematic review, all the elements of the research question should be clearly stated, all relevant studies should be identified, the inclusion criteria should be appropriate and the included studies valid, heterogeneity should be identified, and finally the results of the meta-analyses should be appropriately presented. This paper aims to provide an overview of systematic reviews and meta-analyses. Furthermore, we examine the rationale for conducting such a study, overview the methodology, and highlight pitfalls and weaknesses inherent in the process.