Longitudinal comparison of the Health Assessment Questionnaire (HAQ) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC)

Objective. To compare the measurement properties of the generic Health Assessment Questionnaire (HAQ) and the disease-specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Methods. Physical function, pain, and radiographic progression were assessed in knee or hip osteoarthritis patients (n 271) who had 2 radiographs that were at least 6 months apart from 6 ARAMIS (Arthritis, Rheumatism, and Aging Medical Information System) databanks. Data were compared at baseline and after a mean of 3.2 (SE 0.10) years. Correlation coefficients and standardized effect sizes (SES) were used to assess their relationship and responsiveness. Results. The majority of items in the 2 function and pain scales overlapped and were highly and significantly correlated with each other at baseline and last assessments (function at baseline r(s) = 0.71 and function at last assessment r(s) = 0.79, P < 0.0001; pain at baseline r(s) = 0.70 and pain at last assessment r(s) = 0.76, P < 0.0001). The HAQ disability index and total knee score were more sensitive to detection of disease progression than the WOMAC (SES for HAQ = 0.27; SES for WOMAC = -0.05). Conclusion. Both instruments showed favorable measurement properties, with the HAQ having the advantages of being more sensitive to change and adaptable to a wide variety of diseases and conditions, which contribute to the generalizability of findings.