To determine the content validity, the construct validity, and the responsiveness of the Dutch McMaster Toronto Arthritis Patient Preference Questionnaire (MACTAR) in patients with osteoarthritis (OA) of the hip or knee.
The MACTAR comprises 2 parts: a transitional part and a status part. Content validity was investigated by comparing patient-elicited activities to items on the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the Medical Outcomes Study Short-Form 36 (SF-36). Construct validity was determined by correlating MACTAR outcomes with WOMAC/SF-36 outcomes. Responsiveness was investigated by correlating MACTAR, WOMAC, and SF-36 change scores with patient global assessment (PGA) scores and plotting a receiver-operating characteristics (ROC) curve.
Eleven percent of the 894 impaired activities, identified by 192 patients, were not represented in either the WOMAC or the SF-36. The correlations (r(s)) investigated for the MACTAR transitional part varied between 0.27 and -0.40; the status part correlated moderately with the general health scale of the SF-36 (r(s) = 0.44). MACTAR change scores correlated better with PGA than with WOMAC/SF-36 change scores. The area under the ROC curve amounted to 0.90.
Our results suggest that the MACTAR exhibits moderate construct validity and good responsiveness in a population of patients with OA of the hip or knee. The MACTAR is potentially better able to detect changes over time in activities that are important to individual patients compared to other tools measuring physical function (WOMAC, SF-36). Clinicians could use the MACTAR to evaluate clinically relevant changes over time in patient-specific physical functioning.