Patient outcomes in longitudinal observational studies (POLOS) of rheumatoid arthritis: Determining the OMERACT core domain set.

Objective: To define and select rheumatoid arthritis (RA)-specific core domain set for Longitudinal Observational Studies (LOS) within the Outcome Measures in Rheumatology (OMERACT) framework.

Methods: A three-round online Delphi exercise, including patient research partners (PRPs) and other community partners in healthcare, was conducted. Domains scored 7-9 (i.e., critically important to include) by ≥ 70 % of participants in both groups were included. Items were consolidated in a subsequent dedicated meeting.

Results: Nineteen domains scored ≥ 70 % consensus in both groups. The focus group refined these into a list of twelve domains.

Conclusion: The achieved consensus will inform the next steps of developing the core domain set for LOS in RA.