Abstract
Objective To compare five Health Assessment Questionnaire (HAQ) scoring methods to measure functional disability among people with systemic sclerosis (SSc, scleroderma).
Methods Scleroderma Patient-centered Intervention Network Cohort participants completed the Health Assessment Questionnaire (20 items, 8 domains) at enrolment. We calculated HAQ Disability Index (HAQ-DI) scores, which sum the highest item score for each domain and account for the use of aids, devices, or assistance; Alternative Disability Index (HAQ-ADI) scores, which are calculated similarly but do not account for aids, devices, or assistance; Modified HAQ (MHAQ) scores, which are based on one administered item from each domain, as well as a simple summed score of all 20 items. We then compared these scores and those generated from an Item Response Tree (IRTree) on convergent validity with physical function, pain interference, and hand function using Pearson's correlations.
Results IRTree-based scores were highly correlated (r = 0.90 to 0.95) with other scoring procedures and showed moderate-to-strong correlations with all external measures (r = 0.68 to 0.80). There was no evidence of a difference between IRTree-based and HAQ-DI correlations with external measures. IRTree-based scores performed better than HAQ-ADI, MHAQ, and summed scores for physical function and pain interference but worse for hand function.
Conclusion IRTree-based scoring is a novel approach that incorporates information from all HAQ items and whether participants use aids, devices, or assistance. Its association with external measures, however, did not differ from the standard HAQ-DI. HAQ-DI scoring is easy to implement, and extensive comparative data are available, making it the preferred scoring method.
