Confirmation of the Validity of the HAQ-DI in Two Populations Living With Chronic Illnesses

Abstract

The assessment of functional health in chronic illnesses such as HIV/AIDS and rheumatoid arthritis is central to the measurement of health-related quality of life. The purpose of this article is to report the testing and comparison of the measurement structure of the Health Assessment Questionnaire-Disability Index (HAQ-DI), a measure of functional health, in 917 persons living with HIV/AIDS and 901 individuals with rheumatoid arthritis. The samples come from data collected as part of the Arthritis, Rheumatism, and Aging Medical Information System (ARAMIS) and AIDS Time-Oriented Health Outcome Study (ATHOS) projects. Using confirmatory factor analysis (CFA), the hypothesized structure represented by a general factor (functional health) and eight measured items was tested separately. Based on the fit indexes, the model fit the ATHOS data (χ2 = 36.933, p < .0117; CFI = 1.000; SRMR = 0.025). After correlating the error terms for two of the measured items, the model also fit the ARAMIS data (χ2 = 302.34, p = .0000; CFI = 0.937; SRMR = 0.041). This analysis provides further support of the construct validity of the HAQ-DI for persons living with HIV/AIDS or rheumatoid arthritis.