Adaptation and validation of the Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) questionnaire for use in patients with osteoarthritis in Spain.

This study aims to adapt and validate the Spanish version of the Osteoarthritis Knee and Hip Quality of Life (OAKHQOL) questionnaire. The OAKHQOL was adapted into Spanish using a forward-backward translation methodology. The Spanish version was then validated in a prospective, mixed-design study of 759 patients with hip or knee osteoarthritis (OA). Patients completed the OAKHQOL, Short Form 36 (SF-36), Western Ontario and McMaster Universities Osteoarthritis Index, and the EQ-5D. The internal consistency was evaluated using Cronbach's alpha. Convergent validity was assessed by examining correlations between the OAKHQOL and other patient-reported instruments; known groups' validity was assessed by determining the capacity of the OAKHQOL to discriminate between patients with different levels of disease severity measured using the Lequesne Index. Test-retest reliability was evaluated by calculating the intraclass correlation coefficient (ICC) for all OAKHQOL domains in 409 stable patients with OA. Responsiveness was evaluated by calculating effect sizes among 129 patients undergoing hip or knee replacement. Cronbach's alpha for the five domains of the OAKHQOL ranged from 0.60 to 0.93 while ICCs ranged from 0.75 to 0.81 for all domains except the two social domains. Statistically significant differences (p < 0.001) were observed between patients with different degrees of disease severity on all domains except "social support". The instrument showed convergent validity among hypothesized domains (p < 0.001). Results of the study supported that the Spanish version OAKHQOL questionnaire was a valid instrument to measure health-related quality of life in patients with OA of the lower limb.