A systematic review is a type of study that comprehensively review all other relevant studies on a specific research question or clinical topic. On the hierarchy of evidence — the weakest evidence to the strongest evidence in terms of methodology — systematic reviews are second highest, just under meta-analyses. During a systematic review, researchers review and combine all the information from published and unpublished studies they have identified that meet pre-defined criteria. They involve five steps: framing a question; identifying the relevant research; assessing the quality of the studies; summarizing the evidence; and interpreting the findings.
