The rheumatoid arthritis (RA) core outcome set identifies a minimum set of outcome domains to measure and report in clinical trials. Using a standarized set helps researchers compare findings across studies and understand the effects of interventions.

The original set developed in 1992 recommended joint tenderness, joint swelling, pain, patient and physician global assessments, physical function, and systemic inflammation. Assessment of structural damage using joint radiographs is recommended for studies lasting one year or more. Researchers can include additional outcomes relevant to their study’s objectives.

Patient involvement subsequently highlighted the importance of fatigue, which can affect daily life and provide information beyond other commonly measured outcomes. At OMERACT 8, participants endorsed measuring fatigue in RA studies whenever possible, alongside the existing core set.