Systematic and other reviews: criteria and complexities

Review articles do not require institutional review board approval if the data reviewed are public (including private and government databases) and if the articles reviewed have received institutional review board approval previously. The type of systematic review, according to the Cochrane Collaboration, is based on the research question being asked, and may assess diagnostic test accuracy, review prognostic studies evidence, evaluate intervention effects, scrutinise research methodology or summarise qualitative evidence.6 In the methods section, the participants, interventions, comparisons, outcomes and study design (‘PICOS’) must be put forward. Details regarding the following aspects also should be reported: electronic search strategy (with a full description of at least one electronic search strategy sufficient to allow replication of the search), process for article selection, data variables sought, assumptions and simplifications, methods for assessing bias risk of each individual study (such as selective reporting in individual studies) and utilisation of this information in data synthesis, principal summary measures (e.g. risk ratio, hazard ratio, difference in means), methods of data management and combining study results, outcome level assessment, and any other information. Studies that lack a control group may over-estimate the effect size of the experimental intervention or condition being studied, and are not ideal for meta-analyses.8 It also should be remembered that the conclusions of a meta-analysis are only as valid as the data on which the analysis is based.