LAUSR

To cite: Thomas ET, Heneghan C. BMJ EvidenceBased Medicine Epub ahead of print: [please include Day Month Year]. doi:10.1136/ bmjebm-2021-111845 © Author(s) (or their employer(s)) 2022. No commercial reuse. See rights and permissions. Published by BMJ. Background Clinical trials reduce uncertainties about the benefits and harms of an intervention. Outcomes of interest should be specified before the trial starts (a priori), and clinically relevant to patient care. Selective reporting of prespecified outcomes based on the nature and direction of the analysed results occurs among a large proportion of published clinical trials. Selective outcome reporting bias can potentially compromise the validity of a trial and any subsequent metaanalyses. Selective outcome reporting can occur in different ways: 1. Omitting outcomes which are deemed to be unfavourable or not statistically significant. 2. Adding new outcomes based on collected data to favour statistical significance. 3. Including only a subset of the analysed data in the published study. 4. Failing to report data that was analysed in the trial (such as adverse effects). 5. Changing outcomes of interest (from primary outcomes to secondary outcomes if they do not yield significant results or the desired direction and magnitude of effect). Detecting outcome reporting bias can be difficult. When the clinical trial protocol or the trial registration outcomes of interest differ from the outcomes in the published paper, it constitutes selective outcome reporting bias.