Use of composite outcomes facilitate core outcome set uptake in rheumatoid arthritis trials

The WHO and the International League of Associations for Rheumatology set of core outcomes for rheumatoid arthritis (hereafter RA-COS) was adopted in 1993; it comprises eight individual outcomes which aim to assess disease activity, patient-reported outcome and damage.1 2 In addition, several validated composite outcome measures are available for use in clinical trials to measure both disease activity and state. The two key indices used in RA, the American College of Rheumatology (ACR) 20% and the Disease Activity Score (DAS) 28, represent combined subsets of the core outcome set (COS); they have been widely adopted as primary endpoints, and reporting of one of these, as well as the RA-COS, is recommended in regulatory guidance.3 4 Non-reporting of the individual core outcomes restricts meta-analyses, might lead to relevant information being missed, to exaggerated perceptions on how well an intervention works, and could lead to suspicion of intentional …