Using behavioural science to enhance use of core outcome sets in trials: protocol.

Background: Core outcome sets (COS) represent agreed-upon sets of outcomes, which are the minimum that should be measured and reported in all trials in specific health areas. Use of COS can reduce outcome heterogeneity, selective outcome reporting, and research waste, and can facilitate evidence syntheses. Despite benefits of using COS, current use of COS in trials is low. COS use can be understood as a behaviour, in that it is something trialists do, or not do, adequately. The aim of this study is to identify strategies, informed by behaviour change theory, to increase COS use in trials.

Methods: The project will be conducted in two stages, informed by the behaviour change wheel (BCW). The BCW is a theoretically based framework that can be used to classify, identify, and develop behaviour change strategies. In Stage 1, barriers and enablers to COS use will be extracted from published studies that examined trialist's use of COS. Barriers and facilitators will be mapped to the components of COM-B model (capability, opportunity, and motivation), which forms part of the BCW framework. Stage 2 will build on Stage 1 findings to identify and select intervention functions and behaviour change techniques to enhance COS use in trials.

Discussion: The findings of this study will provide an understanding of the behavioural factors that influence COS use in trials and what strategies might be used to target these factors to increase COS use in trials.