In osteoarthritis (OA) clinical trials, a pain measure that is most sensitive to change is considered optimal. We compared sensitivity to change of patient-reported pain outcomes, including a patient-preference measure (where the patient nominates an activity that aggravates their pain).
We used data from 2 trials of patients with confirmed (American College of Rheumatology criteria) knee OA: a trial of brace treatment for patellofemoral OA, and a trial of intraarticular steroids in knee OA. Both trials reported an improvement in pain following treatment. Participants rated pain on a 100-mm visual analog scale (VAS), in the activity that caused them the most knee pain (VASNA ), as well as completing questions on overall knee pain and the Knee Injury and Osteoarthritis Outcome Score (KOOS) questionnaire. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) scores were also calculated from the KOOS. Standardized changes in each outcome were generated between treatment and control after 6 weeks intervention in the BRACE trial, and 1-2 weeks following intervention in the steroid trial.
The VASNA produced standardized changes following treatment that were at least as large as other pain outcomes. In the BRACE trial, the between-groups standardized change with the VASNA was -0.63, compared with the KOOS pain subscale change of -0.33, and pain in the last week VAS change of -0.56. In the steroid study, within-group change following treatment in the VASNA was -0.60, compared to the last week VAS change of -0.51, and KOOS pain subscale change of -0.58.
Pain on nominated activity appears to be at least as, and in some cases more, sensitive to change than the KOOS/WOMAC questionnaire.