Comparison of the responsiveness and relative effect size of the western Ontario and McMaster Universities Osteoarthritis Index and the short-form Medical Outcomes Study Survey in a randomized, clinical trial of osteoarthritis patients

Abstract

Objective: This study compares the responsiveness and relative effect sizes of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) with the Medical Outcomes Study Short Form Health Survey (SF-36) in a randomized clinical trial for treatment of osteoarthritis (OA).

Methods: Patients with OA of the knee or hip were randomized to receive either placebo or 2,400 mg/day of ibuprofen for 28 days. Patients completed the WOMAC and SF-36 at baseline and days 7, 14, and 28 of the trial.

Results: Patients receiving ibuprofen showed significant improvement in WOMAC pain, physical functioning, and the total score, while improvement was detected only for bodily pain on the SF-36. The WOMAC detected significant differences between ibuprofen and placebo for pain and physical functioning, whereas the SF-36 detected differences for the bodily pain subscale.

Conclusion: These results suggest the WOMAC has greater power to detect treatment differences than the SF-36, with respect to pain and physical functioning, in OA clinical trials.