Diagnostic Performance of the Multi-Biomarker Disease Activity (MBDA) Score for Rheumatoid Arthritis in Patients with New-Onset Joint Symptoms: An Age-Stratified Retrospective Study.

Purpose: Anti-citrullinated protein antibodies (ACPA) positivity decreases in elderly-onset rheumatoid arthritis (EORA), likely due to immunosenescence and clinical heterogeneity. This study aimed to evaluate the multi-biomarker disease activity (MBDA) score as an alternative diagnostic marker for rheumatoid arthritis (RA) in patients with new-onset joint symptoms, focusing on ACPA-negative cases stratified into young-onset RA (YORA) and EORA. Patients and Methods: This retrospective study was conducted at two institutions in Hokkaido, Japan (2018-2022). Patients with new-onset joint symptoms who had not received prior RA therapy were included. Baseline serum samples were analyzed for MBDA and high-sensitivity C-reactive protein (hsCRP). Diagnostic performance for RA was evaluated using sensitivity, specificity, accuracy, area under the curve, and logistic regression. Results: Among 257 patients, 90 were <60 years (RA, n = 42) and 167 were ≥60 years (RA, n = 84). In YORA, ACPA was the strongest predictor (odds ratio [OR]: 170.48, Conclusion: MBDA, particularly when combined with hsCRP, provides clinically meaningful diagnostic value for RA in patients with new-onset joint symptoms, particularly in ACPA-negative YORA and EORA. Trial Registration: This study was retrospectively registered in the University Hospital Medical Information Network (UMIN000057829).