ABSTRACT
The validity of the Health Assessment Questionnaire (HAQ) functional ability instrument was tested in 120 women with definite systemic lupus erythematosus (SLE) from rheumatology clinics at 2 local tertiary care institutions. Reliability and validity results for this population of women (mean age: 41 years +/- 13; age at diagnosis 33 years +/- 13) indicate that (1) the HAQ was internally reliable (standardized alpha = 0.9443) with no interitem correlation exceeding (r = 0.75); (2) confirmatory factor analysis identified 2 predominant factors among the HAQ components suggestive of large limb gross movements (e.g., walking, arising) and small limb fine movements (e.g., the ability to eat and firmly grip objects). Cumulatively, the 2 factors accounted for 64% of the variation in HAQ ability response. The HAQ response was also valid when compared to the overall disability index (r = 0.65 to 0.82) and other common disease variables that were reported by the patient and collected by the physician at the time of clinical examination. In addition, when stratified by active and inactive disease as defined by the Lupus Activity Criteria Count, inactive patients reported lower disability components (dress, arise, eat, walk, hygiene, reach, grip and activity) than active patients. These findings confirm the valid use of the HAQ as a measure of disability, when compared with other clinical measures of disease status and activity, in female patients with SLE.