At the top of the evidence hierarchy tree discussed in Chapter 7 lies the systematic review. Systematic reviews of randomised clinical trials (RCTs) developed after it was realised that traditional reviews were done in quite arbitrary ways. They are to some extent synonymous with evidence-based dermatology (EBD) in that they inform practitioners on treatment efficacy and harms. Systematic reviews, such as those produced by the Cochrane Collaboration, summarise accurate, up-to-date, high-quality external evidence of the effectiveness of interventions for treating and preventing human disease.2 Put more simply, systematic reviews can be thought of as the science of summarising other studies. The key difference from other more traditional reviews is in the word systematic. Just as those conducting clinical trials follow an explicit and exhaustive protocol of clearly laid-out steps to conduct their trial, systematic reviewers describe precisely how they will search, appraise and synthesise data concerning a specific clinical question. This explicit structure and methodology means that another researcher could replicate the review if necessary. As Chapter 8 emphasises, systematic reviews are done systematically along a series of well-defined steps that are outlined in a protocol. Another important advantage is that some reviews, such as those
conducted within the Cochrane Collaboration, are updated as new evidence and criticisms become available.
Traditional expert reviews are fine for raising issues for discussion, but they are less suitable for summarising treatment efficacy. The unsystematic approach used in such traditional reviews often means that they are more prone to bias and hidden agendas.3 We have all done this in our "traditional" review articles in the past, and I admit having used the "file drawer" method to search for articles for my review of atopic eczema in 1995 (Figure 54.1).4
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