ROB-ME: a tool for assessing risk of bias due to missing evidence in systematic reviews with meta-analysis.

Various methods are available to help users assess whether selective non-publication of studies or selective non-reporting of study results has occurred, but not its impact on a meta-analysis. This limitation of existing methods leaves users to decide their own approach for judging the risk of bias in a meta-analysis result. In this paper, Page and colleagues describe the ROB-ME (risk of bias due to missing evidence) tool, a structured approach for assessing the risk of bias that arises when entire studies, or particular results within studies, are missing from a meta-analysis because of the P value, magnitude, or direction of the study results. The tool is anticipated to help authors and users of systematic reviews identify meta-analyses at high risk of bias and interpret results appropriately.