Reading and critically appraising systematic reviews and meta-analyses: A short primer with a focus on hepatology

Abstract

Systematic review and meta-analysis are fundamental to evidence-based health practice. Their development has paralleled the rapid growth of the biomedical literature and the need to make inferences from an often varied and complex body of knowledge. Identifying and correctly interpreting a body of evidence relevant to a particular clinical question is a daunting challenge for busy clinicians. By contrast, a carefully conducted systematic review can greatly facilitate an understanding of the available evidence. The purpose of this review is to inform the reader about the basics of how systematic reviews are conducted and how to interpret their results. We summarize the major methodologies used in systematic reviews (Table 1) and the issues related to their conduct and interpretation. Systematic review is a rigorous process designed to comprehensively identify eligible studies pertaining to a specific question, appraise them, and present key findings and limitations [1–3]. It provides a framework to scrutinize a body of knowledge and describe in detail the variability in results and factors that may account for it. Meta-analysis, which is commonly included in systematic reviews, is a process where results from different studies are combined quantitatively. It can provide an overall estimate of the net benefit or harms, even when these may not have been apparent in individual studies [4]. Systematic reviews contrast with traditional ‘narrative’ reviews and textbook chapters, which, generally, do not exhaustively review the literature, may be biased or lack transparency in the selection and interpretation of supporting evidence, and usually do not provide a quantitative synthesis of the data [5].