Toward development of a fibromyalgia responder index and disease activity score: OMERACT module update.

Following development of the core domain set for fibromyalgia (FM) in Outcome Measures in Rheumatology Clinical Trials (OMERACT) meetings 7 to 9, the FM working group has progressed toward the development of an FM responder index and a disease activity score based on these domains, utilizing outcome indices of these domains from archived randomized clinical trials in FM. Possible clinical domains that could be included in a responder index and disease activity score include pain, fatigue, sleep disturbance, cognitive dysfunction, mood disturbance, tenderness, stiffness, and functional impairment. Outcome measures for these domains demonstrate good to adequate psychometric properties, although measures of cognitive dysfunction need to be further developed. The approach used in the development of responder indices and disease activity scores for rheumatoid arthritis and ankylosing spondylitis represents heuristic models for our work, but FM is challenging in that there is no clear algorithm of treatment that defines disease activity based on treatment decisions, nor are there objective markers that define thresholds of severity or response to treatment. The process of developing candidate dichotomous responder definitions and continuous quantitative disease activity measures is described, along with participant discussions from OMERACT 10. Final results of this work will be published in a separate report pending completion of analyses.