Responsiveness of the OARSI-OMERACT osteoarthritis pain and function measures

To assess the responsiveness of the Intermittent and Constant Osteoarthritis Pain (ICOAP) measure, Hip Disability and Osteoarthritis Outcome Score Physical Function Short Form (HOOS-PS), and the Knee Disability and Osteoarthritis Outcome Score Physical Function Short Form (KOOS-PS) in a pharmacological trial.

Data were obtained from a randomized double-blind trial comparing naproxcinod with naproxen and ibuprofen in individuals with hip or knee osteoarthritis (OA) (NCT00662896). Participants completed the ICOAP, HOOS-PS/KOOS-PS, and Western Ontario and McMaster Universities OA Index (WOMAC) Likert version 3.0 before and 13 weeks after treatment. In hip and knee OA participants separately, the mean pre-post treatment change in scores, effect size (ES) and standardized response mean (SRM) were determined for each measure by treatment arm, and for all arms combined.

Of 349 trial participants, 156 with knee OA and 48 with hip OA completed all measures at both time-points and were included (mean age 61 years; two-thirds female). Although there was both within treatment and between treatment variability in response, among knee OA participants, ICOAP intermittent, constant, and total scores and KOOS-PS scores showed, on average, moderate effects, with ESs ranging from 0.46 to 0.54 and SRMs from 0.49 to 0.56. Similar changes were seen for the WOMAC pain and function subscales (0.58 and 0.58, respectively). In those with hip OA, no significant improvement in symptoms was seen for any measure.

Responsiveness to pharmaceutical intervention was demonstrated for ICOAP and KOOS-PS among participants with knee OA. Absence of treatment response precluded assessment of responsiveness in hip OA.