Reporting bias

Reporting bias is the tendency for authors to selectively use information or outcomes from investigations or trials based on certain characteristics. The dissemination of research findings may, therefore, be influenced by the nature and direction of the results. Different types of bias due to the nature and direction of results include: ‘publication bias’ (likelihood of publication of research); ‘time lag bias’ (delaying or expediting publication of research), ‘citation bias’ (citing or not citing research), and ‘outcome reporting bias’ (selective reporting of outcomes). Recently, there have been initiatives, such as clinicaltrials.gov, to minimise this type of bias by ensuring that clinical trials (especially those of new medicines, for which marketing authorisation will be sought) are entered prospectively on registers so that their status and results are available, especially for systematic reviews of efficacy supporting health technology assessment.