A survey of knowledge, perceptions and use of core outcome sets among clinical trialists

Core outcome sets (COS) are standardised sets of outcomes, which represent the minimum outcomes that should be measured and reported in clinical trials. COS can enhance comparability across health trials by reducing heterogeneity of outcome measurement and reporting and potentially minimising selective outcome reporting. Examining what researchers involved in trials know and think about COS is essential to increase awareness and promote COS uptake. The aim of this study is therefore to examine clinical trialists' knowledge, perceptions and experiences of COS.

An online survey design was used. Participants were clinical trialists, operationalised for the current study as researchers named as the contact person on a trial registered on the International Standard Randomised Controlled Trial Number (ISRCTN) Trial repository between 1 January 2019 and 21 July 2020. Survey items assessed clinical trialists' familiarity with and understanding of COS, along with experiences of COS use and development.

Of 1913 clinical trialists contacted to participate, 62 (3%) completed the survey. Forty (65%) participants were familiar with COS and, of those familiar with COS, 21 (55%) had been involved in a trial that used a COS. Of clinical trialists who used COS in a trial(s), less than half (n = 9, 41%) reported that all COS outcomes were used. The main barriers to using COS are poor knowledge about COS (n = 43, 69%) and difficulties identifying relevant COS (n = 42, 68%). Clinical trialists also reported perceptions of COS as restrictive and often containing too many outcomes. The main enablers to using COS are clear understanding (n = 51, 82%) and perceived importance of COS (n = 44, 71%).

Enhancing clinical trialists' use of all COS outcomes is needed to reduce outcome heterogeneity and enhance comparability across trial findings. Enhancing awareness of COS importance among researchers and funders is needed to ensure that COS are developed and used by clinical trialists. Education and training may further promote awareness and understanding of COS.