Importance of large joint involvement in functional disability of patients with rheumatoid arthritis

Abstract

<p><strong>Objectives: </strong>The Health Assessment Questionnaire (HAQ) identifies reversible activity-related factors (ActHAQ) and ones that are irreversible due to joint damage (DamHAQ). We aimed to examine which joints are associated with ActHAQ and DamHAQ from the viewpoint of affected joint size and distribution.</p><p><strong>Methods:</strong> Data from 7,408 patients who had not undergone orthopedic surgery were extracted from the National Database of Rheumatic Diseases by iR-net in Japan (<em>NinJa</em>) database. The regression coefficient between the HAQ and the Simplified Disease Activity Index (SDAI) was 0.036 in 141 patients with very early rheumatoid arthritis (RA) whose DamHAQ is presumed to be zero. We calculated the two components of the HAQ using the following formulas: ActHAQ = 0.036 × SDAI and DamHAQ = HAQ – ActHAQ.</p><p><strong>Results:</strong> Large joint involvement was positively correlated with both ActHAQ and DamHAQ. Although upper/small joint involvement was the most significant predictor of ActHAQ elevation, it was inversely correlated with DamHAQ. Lower/small joint involvement was not a significant factor in either component.</p><strong>Conclusions:</strong> Compared to small joints, large joint involvement was associated with an increase in damage-related HAQ. In light of this finding, large joint involvement should be thoroughly treated to prevent RA patients from experiencing worsening physical function.