Patient-preference disability assessment for disabling knee osteoarthritis: Validity and responsiveness of the McMaster-Toronto Arthritis Patient Preference Disability Questionnaire.

BACKGROUND: The McMaster-Toronto Arthritis Patient Preference Disability Questionnaire (MACTAR) measurement of function may be more comprehensive and add useful information about disability than traditional fixed-item questionnaires, especially about issues that really matter to the patient, for developing personalized medicine.

OBJECTIVES: We aimed to assess priorities in disability and restriction in participation in patients with disabling knee osteoarthritis (OA) by the MACTAR and evaluate its validity and responsiveness.

METHODS: We evaluated 127 in- and outpatients with knee OA in two tertiary care teaching hospitals between August 2010 and July 2012 by using the MACTAR, the Western Ontario and McMaster Universities Osteoarthritis Index, Lequesne scale, Fear Avoidance Beliefs Questionnaire, a life satisfaction score and pain, global assessment of disease activity and functional impairment scores on a numerical rating scale. Validity was assessed by Pearson correlation and responsiveness by the standardized response mean (SRM) and effect size (ES).

RESULTS: Patients ranked 35 different activities by the MACTAR; the 3 domains of the International Classification of Functioning, Disability and Health most often identified were mobility (cited 233 times, 52.3%); community, social and civic life (cited 122 times, 27.4%); and domestic life (cited 64 times, 14.4%). The MACTAR score was best correlated with functional impairment (r=0.5). Convergent and divergent validity was as expected. In all, 108 patients completed a 6-month follow-up evaluation: 27 patients shifted their priorities at 6 months, for a decrease in SRM and ES. The SRM (0.64) and ES (0.92) for the MACTAR without shifts in priorities were the highest among the outcome measures tested; for patients considering their condition improved, the values were 0.85 and 1.17, respectively.

CONCLUSIONS: For assessing priorities in disability and restriction in participation among patients with knee OA, the MACTAR has acceptable validity and responsiveness.