Evidence suggests that inflammation has a harmful effect on muscle strength as well as on functional disability. The purpose of the present study was to examine the association of objectively measured disease activity levels and functional disability among Iranian patients with Rheumatoid Arthritis (RA), and to analyse whether a Persian version of the health assessment questionnaire-disability index (PHAQ-DI) can distinguish between RA patients at different stages of the disease progression.
198 RA patients were requested to complete the PHAQ-DI. The disease activity score for each patient was evaluated using the disease activity score (DAS-28). The association analysis between the PHAQ-DI scores and the four levels of disease activity was measured using a Spearman correlation coefficient. A Kruskal-Wallis analysis was utilized to determine differences in PHAQ-DI scores among the levels of disease activity. The Receiver operating characteristic (ROC) curve was also utilized to determine the PHAQ-DI total score cut-off for predicting the level of disease activity.
Spearman's correlation coefficients between the PHAQ-DI and the disease activity level ranged between 0.59 and 0.75. There were significant differences in the PHAQ-DI total score among known groups with various disease activity levels (P = 0.001); However, HAQ-DI total score could not differentiate the remission phase from low disease activity levels in patients with RA (p = 0.37). The PHAQ-DI total score cut-off for distinguishing remission-low disease activity from moderate-high disease activity was 1.19, with a specificity of 0.91 and a sensitivity of 0.615.
The present findings provide evidence for the degree to which the PHAQ-DI measures identify and distinguish disease activity levels in patients with rheumatoid arthritis. The PHAQ-DI questionnaire, as a patient-administered, non-invasive, fast, inexpensive and available tool, can be used in the rheumatologist's office as a substitute for determining disease activity in patients with active RA.