Physical function continues to improve when clinical remission is sustained in rheumatoid arthritis patients

INTRODUCTION: To investigate the course of functional status assessed by health assessment questionnaire (HAQ) in rheumatoid arthritis (RA) patients with sustained clinical remission (REM). METHODS: In recent RA clinical trials, we identified patients with subsequent visits of ≥24 weeks in clinical REM according to the disease activity score using 28-joint counts including C-reactive protein (DAS28) (≤2.6), or simplified disease activity index (SDAI) (≤3.3). Area under the curve (AUC) and mean HAQ scores throughout the time in sustained REM were compared using t test, analyses of variance (ANOVA) and adjusted general linear modeling (GLM) with repeated measures. In Cox regression analyses, the time to regain full physical function was modeled. Sensitivity analyses were performed in patients of sustained SDAI low disease activity (LDA; SDAI ≤11). RESULTS: A total of 610 out of 4364 patients achieved sustained DAS28 REM (14 %) and 252 SDAI REM (5.8 %). ANOVA testing for linear trend showed significant decrease of mean HAQ from week 0 (start of REM) to week 24, regardless of REM criteria used. AUC of HAQ throughout 24 weeks of REM was higher in DAS28 compared to SDAI REM (p ≤0.01). GLM adjusting for covariates showed significant decrease of monthly HAQ scores from week 0 to 24 (DAS28: 0.276, 0.243, 0.229, 0.222, 0.219, 0.209 to 0.199; p = 0.0001; SDAI: 0.147, 0.142, 0.149, 0.129, 0.123, 0.117 to 0.114; p = 0.029). Similarly, a decrease of HAQ over time was found in patients of sustained SDAI LDA. In DAS28 REM, the chance of regaining full physical function was higher for female (hazard ratio HR [95 % confidence interval]: 1.41 [1.13–1.76]) and early RA patients (disease duration ≤2 years: HR 1.29 [1.01–1.65]); in SDAI REM no significant differences were found. CONCLUSIONS: Physical function continues to improve if the target of REM or LDA is sustained. The stringency of the remission criteria determines achievement of the best possible functional improvement. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13075-015-0719-x) contains supplementary material, which is available to authorized users.