Abstract
Objectives To investigate whether the Health Assessment Questionnaire Disability Index (HAQ-DI) reflects objective measures of physical function in people with osteoarthritis (OA) and rheumatoid arthritis (RA). Methods In total, 139 people, 71 with RA fulfilling the American College of Rheumatology (ACR) criteria (1987) and 68 with OA fulfilling ACR criteria for OA of the hip or knee, completed the HAQ-DI. Physical function was assessed using Timed Up and Go (TUG), 30 seconds Sit to Stand (STS), grip strength dynamometry and pedometer steps over 7 days. Results The strongest association with HAQ-DI was with the TUG (R-2 of 0.671 and 0.512 in RA and OA groups, respectively). HAQ-DI and STS showed a non-linear association in both groups with R-2 of 0.380 in RA and 0.359 in OA. A strong association was found between HAQ-DI and grip strength in the OA group (R-2 = 0.681), whereas the RA group showed a moderate association (R-2 = 0.285). There was a strong association between the HAQ-DI and pedometer measures in RA (R-2 = 0.562), although this association was weak in OA (R-2 = 0.156). Conclusion The HAQ-DI has a strong association with the TUG in both RA and OA. There was variable association between the HAQ-DI and other physical performance measures, as well as differences between the RA and OA cohorts. In order to form a full and accurate clinical picture, health professionals should perform both subjective patient-reported outcome measures and objective physical performance measures of disability.