The importance of measuring hand and foot function over the disease course in rheumatoid arthritis: An eight‐year follow‐up study

Objective: To assess function using the Signals of Functional Impairment (SOFI) instrument over 8 years, to study clinical variables associated with the change, and to study change over time of the SOFI items. Methods: In total, 1,223 patients with early rheumatoid arthritis (RA) from the Better Anti-Rheumatic Farmacotherapy (BARFOT) cohort (mean ± SD age 56.9 ± 15.4 years, 67% women) were included in the analysis. Data from baseline and from 1 and 8 years were studied. The SOFI instrument includes measures of range of motion in the hand, shoulder/arm, and lower extremity (range 0–44, best to worst). The effects of baseline variables (sociodemographic, disease activity, joint destruction, and function) on change in SOFI scores were studied by linear regression analysis. Results: During the first year, the improvement in mean ± SD SOFI scores was 2.7 ± 5.7 (P < 0.001). Worse scores in the Disease Activity Score in 28 joints and Health Assessment Questionnaire score at baseline were associated with this improvement (r2 ≤ 0.11). During the next 7 years, the deterioration in SOFI scores was mean ± SD 1.5 ± 4.9 (P < 0.001). Based on change scores, we found that finger flexion, pincer grip, and toe-standing were the most important items to measure, explaining 58–61% of the total SOFI score, and these items were also associated with radiographic changes at the 8-year follow-up. Conclusion: Function as assessed with SOFI scores improved during the first year in patients with early RA, but it deteriorated slowly thereafter. Impaired hand and foot function was associated with joint destruction at the 8-year follow-up. Measures of hand and foot function will complement self-reported and medical data, both in clinical work and in long-term research studies.