Feasibility and Face Validity of Outcome Measures for Use in Future Studies of Polymyalgia Rheumatica: An OMERACT Study

OBJECTIVE: To survey participants with polymyalgia rheumatica (PMR) to evaluate the face validity, acceptability, and domain match of proposed candidate outcome measures.

METHODS: A structured, online, anonymous survey was disseminated by patient support groups through their networks and online forums. The candidate outcome measures comprised (1) visual analog scale (VAS) and numerical rating score (NRS) to assess pain; (2) VAS, NRS, and duration to assess stiffness; (3) the modified Health Assessment Questionnaire and Health Assessment Questionnaire Disability Index to assess physical function; and (4) C-reactive protein and erythrocyte sedimentation rate to assess inflammation. Free-text answers were analyzed using descriptive thematic analysis to determine respondents' views of the candidate instruments.

RESULTS: Seventy-eight people with PMR from 6 countries (UK, France, USA, Canada, Australia, and New Zealand) participated in the survey. Most respondents agreed candidate instruments were acceptable or "good to go." Free-text analysis identified 5 themes that participants considered inadequately covered by the proposed instruments. These related to (1) the variability, context, and location of pain; (2) the variability of stiffness; (3) fatigue; (4) disability; and (5) the correlation of inflammatory marker levels and severity of symptoms, sometimes reflecting disease activity and other times not.

CONCLUSION: Participants reported additional aspects of their experience that are not covered by the proposed instruments, particularly for the experience of stiffness and effect of fatigue. New patient-reported outcome measures are required to increase the relevance of results from clinical trials to patients with PMR.