Core domain set for studies of acute calcium pyrophosphate crystal arthritis: OMERACT delphi survey to establish consensus.

Objective: To identify potential domains for the Outcome Measures in Rheumatology (OMERACT) core domain set for studies of an individual flare of acute calcium pyrophosphate (CPP) crystal arthritis.

Methods: Patient research partners (PRPs) and other participants (mainly clinicians and researchers) completed three rounds of survey using Delphi methodology. Consensus was defined as ≥ 70 % of both PRP and other participants groups rated the domain as a 'critically important domain to include'. In a subsequent ranking exercise, all participants were asked to rank and comment on up to 10 domains to include as core domains.

Results: Fourteen domains reached consensus as critically important in the Delphi survey. In the Pathophysiological Manifestations area, the domains were joint pain, joint tenderness, joint swelling, joint inflammation on imaging tests and duration of acute CPP crystal arthritis flare. In the Life Impact area, the domains were overall function, ability to complete daily tasks, ability to work, health related quality of life, patient global assessment response to treatment, patient and physician global assessments of disease activity, and patient satisfaction with treatment. In the Societal/Resource Use area, use of rescue medications reached consensus. In the ranking exercise, joint pain, joint tenderness, joint swelling, overall function and ability to complete daily tasks ranked highest.

Conclusion: Joint pain, joint swelling, joint tenderness, duration of acute CPP crystal arthritis flare, overall function, ability to complete daily tasks, and patient global assessment of disease activity received the strongest support to be included in the OMERACT core domain set for studies of acute CPP crystal arthritis.