Systematic review is a tool used to summarise, appraise and communicate the results and implications of a large quantity of research and information. It is particularly valuable as it can be used to synthesise results of many separate studies examining the same question, which may have conflicting findings. Meta-analysis is a statistical technique that may be used to integrate and summarise the results from individual studies within the systematic review, to generate a single summary estimate for the effect of an intervention on a subject.
The purpose of a systematic review is to provide the best available evidence on the likely outcomes of various actions and, if the evidence is unavailable, to highlight areas where further original research is required. It is, therefore, a tool to support decision-making by providing independent, unbiased and objective assessment of evidence; it is not designed to make decisions on behalf of the user-community. For a detailed description of the systematic review process, please refer to the Guidelines for Systematic Reviews in Environmental Management.
Due to its systematic nature, the approach is far more robust and powerful than a traditional literature review, which may be purely narrative, subjective or susceptible to publication bias. A systematic reviewstrives to exhaustively search, recognise and obtain all relevant unpublished grey literature and research findings, in addition to peer-reviewed journal publications. The process of study inclusion into the systematic reviewis entirely transparent, and should therefore be repeatable in its conclusions.