Development and preliminary evaluation of the OsteoArthritis Questionnaire (OA-Quest): a psychometric study: methodological issues.

OBJECTIVE This study reports the development of the OsteoArthritis Questionnaire (OA-Quest) - a new measure designed to comprehensively capture the potentially modifiable burden of osteoarthritis. DESIGN Item development was guided by the a priori conceptual framework of the Personal Burden of Osteoarthritis (PBO) which captures 8 dimensions of osteoarthritis burden (Physical distress, Fatigue, Physical limitations, Psychosocial distress, Physical de-conditioning, Financial hardship, Sleep disturbances, Lost productivity). One hundred and twenty three candidate items were pretested in a clinical sample of 18 osteoarthritis patients. The measurement properties of the OA-Quest were assessed with exploratory factor analysis (EFA), Rasch modelling, and confirmatory factor analysis (CFA) in a community-based sample (n = 792). RESULTS EFA replicated 7 of the 8 PBO domains. An exception was PBO Fatigue domain, with items merging into the Physical distress subscale in the OA-Quest. Following item analysis, a 42-item 7-subscale questionnaire was constructed, measuring Physical distress (seven items, Cronbach's α = 0.93), Physical limitations (11 items, α = 0.95), Psychosocial distress (seven items, α = 0.93), Physical de-conditioning (four items, α = 0.87), Financial hardship (four items, α = 0.93), Sleep disturbances (five items, α = 0.96), and Lost productivity (four items α = 0.90). A highly restricted 7-factor CFA model had excellent fit with the data (χ(2)(113) = 316.36, P < 0.001; chi-square/degrees of freedom = 2.8; comparative fit index [CFI] = 0.97; root mean square error of approximation [RMSEA] = 0.07), supporting construct validity of the new measure. CONCLUSIONS The OA-Quest is a new measure of osteoarthritis burden that is founded on a comprehensive conceptual model. It has strong evidence of construct validity and provides reliable measurement across a broad range of osteoarthritis burden.