Relative importance of the functional abilities comprising Health Assessment Questionnaire Disability Index among rheumatoid arthritis patients.

The aim was to evaluate the relative importance of the 20 functions assessed by patients to produce the Health Assessment Questionnaire's Disability Index (HAQ-DI). A systematic sample of 242 rheumatoid arthritis patients was drawn. Altogether 179 subjects returned acceptably filled questionnaire including perceived rheumatoid arthritis status in the 20 functions comprising the HAQ-DI. A separate complementary questionnaire was sent to 80 randomly chosen subjects. They were asked to estimate how important each of the same 20 items were in their everyday life using the VAS method. Completely answered complementary questionnaires were returned by 66 (88%) of the subsample. The relative importance of the functions assessed varied considerably. Men assessed the highest importance to the ability to walk outdoors on flat ground and women to dressing themselves, getting in and out of bed and washing and drying their body. For both genders the least important function was the ability to take a tub bath. The importance of all other functions except taking a tub bath was positively highly significantly correlated with the importance of each of the other functions. Factor analyses with one factor model showed high loadings on most functions, with the exception of 'Take a tub bath'. The two-factor model formed one factor with loadings concentrating slightly more on 'lower extremity' and another on 'upper extremity'. Assessment of RA patients' functional status would benefit from further development of measures by giving relative weights from patients' perspective to those functional abilities which are used for index computations.