Comparison of the Indian version of Health Assessment Questionnaire Score and Short Form 36 Physical Function Score in rheumatoid arthritis using Rasch analysis

Abstract

Objective The health assessment questionnaire (HAQ) has been modified by many investigators to suit the culture and lifestyle of Indian population and these have been validated using traditional approaches. The goal of this study was to further validate the Indian version of HAQ published in 2002 by modern psychometric analysis, specifically by examining fit of the scale's data to the Rasch measurement model. Methods A cross-sectional study was performed on 46 patients with rheumatoid arthritis (RA) from a single center in western India. Demographic characteristics, pain score and global perception of health were recorded on visual analogue scale. Functional outcome was assessed with the Indian HAQ and Short Form 36 physical function (SF 36-PF). Rasch analysis was performed to examine the property of various measures and to compare them on a common scale. Result The mean age ± SD was 45 ± 14.19 years and mean duration was 35.5 ± 52 months. 82.6% were women. The Indian HAQ highly correlated with SF 36-PF ( r = 0.812, P < 0.001). Both the indices showed a moderate correlation with fatigue, pain, global health perception as well as disease activity scores (DAS28). Both the indices satisfied the Rasch model and were unidimensional with adequate person separation and reliability. Nine out of the 12 items in Indian HAQ were fitting in the Rasch model while in SF 36-PF scale nine out of 10 were fitting in the Rasch model. Three items in the HAQ (a) sitting cross-legged, (b) bending, and (c) lifting a cup were not fitting in the Rasch model, while one item of SF 36 ‘walking one block’, was not fitting in the Rasch model. 2.2% of patients assessed by Indian HAQ had 0 score (floor effect), while none had 3 score (ceiling effect), while 15.2% had maximum SF 36-PF score (ceiling effect) while none had 100 score (floor effect). Conclusion Both Indian HAQ and SF 36-PF provide unidimensional measure of physical functioning in RA. SF 36-PF has significant psychometric advantage over Indian HAQ in RA in our cohort.