Factors associated with discordance between the patient-reported Rheumatoid Arthritis Disease Activity Index (RADAI) and the Simplified Disease Activity Index (SDAI) concerning the achievement of treat-to-target goals – data from the REAL study

Abstract

Abstract Background Treat-to-target (T2T) strategies in rheumatoid arthritis (RA) rely on regular assessment of disease activity using validated composite indices, with remission or low disease activity as therapeutic goals. The Simplified Disease Activity Index (SDAI) is widely recommended for this purpose. With the expansion of telemedicine and patient-centered care, self-administered tools such as the Rheumatoid Arthritis Disease Activity Index (RADAI) have gained relevance. However, discordance between patient-reported and composite disease activity measures may affect the interpretation of T2T achievement. Objective To assess RADAI/SDAI concordance regarding T2T status among patients with RA who had achieved remission or low disease activity according to SDAI (SDAI < 11), and to identify factors associated with discordance. Methods This cross-sectional sub-analysis of the multicenter REAL study included patients with RA from 11 Brazilian public hospitals who had SDAI < 11 at baseline. Participants were classified as concordant when RADAI also indicated achievement of the T2T goal (RADAI < 2.2) and discordant when RADAI indicated moderate or high disease activity (RADAI ≥ 2.2). Logistic regression was used to identify factors independently associated with discordance. Results Among 485 participants with SDAI < 11, 89.9% ( n = 436) were female, 61.2% ( n = 297) were white, and the mean (SD) age was 57.0 (11.4) years. RADAI classification was concordant with SDAI-defined T2T status in 63.9% ( n = 310) and discordant in 36.1% ( n = 175). In multivariable analysis, corticosteroid use (OR 2.62; 95% CI 1.29–5.29; p = 0.007), joint pain intensity (OR 1.05; 95% CI 1.03–1.07; p < 0.001), patient global assessment (OR 1.12; 95% CI 1.08–1.16; p < 0.001), and disability assessed by HAQ (OR 2.32; 95% CI 1.24–4.26; p = 0.006) were independently associated with discordance. Conclusion More than one-third of patients who had achieved SDAI-defined T2T goals were classified by RADAI as having moderate or high disease activity. Discordance was associated predominantly with patient-reported symptoms and functional disability. These findings suggest that SDAI and RADAI capture partially different and complementary dimensions of disease burden and should be interpreted within the broader clinical context. Clinical trial number Not applicable.