To examine the value of the Health Assessment Questionnaire (HAQ) as an outcome measure in short term exercise trials. We studied the association of the objectives of exercise, namely joint mobility, muscle strength, and physical condition, with the HAQ.
Data for 100 patients with rheumatoid arthritis (RA) included in a study to examine the effect of exercise therapy were used for secondary analysis. Disease activity was determined by the disease activity score (DAS3), pain was scored on a visual analog scale (VAS), and depression was measured by the Dutch Arthritis Impact Measurement Scale. Aerobic capacity (VO2max) estimated from a submaximal ergometer test, grip strength (kPa), isokinetic muscle strength of the knee (Nm/kg), and the Escola Paulista de Medicina range of motion (EPM-ROM) score, a measure of general flexibility, were used as indicators for physical impairments. All variables were entered in a forward multiple regression analysis with the HAQ as dependent variable.
The HAQ was significantly correlated with the DAS3 score (r = 0.53), pain (r = 0.51), depression (r = 0.40), joint mobility (r = 0.27), quadriceps strength (r = -0.35), and grip strength (r = -0.50), but not with physical condition. The DAS3 score was first entered in the multiple regression analysis model, followed by pain, quadriceps strength, and grip strength (R2 = 0.45). After 12 weeks of exercise therapy changes in the HAQ were significantly correlated with changes in pain (r = 0.41), in depression (r = 0.33), and in quadriceps strength (r = -0.25), but not with changes in joint mobility or physical condition.
Physical impairments are weakly associated with the HAQ. The HAQ is not an appropriate instrument to detect changes in physical impairments due to short term exercise therapy.