FIGURE 1.
Summary of the study methodology, processes of review, and outcomes of inclusion and exclusion criteria. Reasons for exclusion are detailed online (see “Supplemental data” in the online issue). *Data from 2 reports from the same study at different times (16, 30) were combined before meta-analysis. Literature searches were conducted in week 3 of August 2012. MEDLINE and EMBASE were searched through PROQUEST (http://search.proquest.com) via the Royal Society of Medicine (http://www.rsm.ac.uk; see Search Strategies under “Supplemental data” for details). nr, number of reports; k, number of studies.