Utility of Red Cell Distribution Width in Assessing Disease Activity in Patients with Rheumatoid Arthritis: A Cross-Sectional Study

Background: Rheumatoid arthritis (RA) is a chronic systemic autoimmune disease characterized by synovial inflammation and joint destruction. The Disease Activity Score 28 (DAS28) is widely used to assess disease activity but includes subjective components and requires calculation. A simple, objective, and readily available biomarker would be clinically valuable. Red cell distribution width (RDW), obtained from routine complete blood count testing, has been proposed as a potential inflammatory marker. Objective : To evaluate the utility of RDW in assessing disease activity using DAS28 in patients with RA. Methods: This cross-sectional study included 100 patients with diagnosed RA attending or admitted to Mymensingh Medical College Hospital between December 2023 and September 2025. Disease activity was assessed using DAS28-ESR. RDW-CV and RDW-SD were analyzed in relation to disease activity categories. Correlation analysis and receiver operating characteristic (ROC) curve analysis were performed to evaluate the discriminative ability of RDW parameters. Results: Patients with moderate-to-severe disease activity had significantly higher ESR, CRP, RDW-CV, RDW-SD, and ferritin levels, and lower serum iron and transferrin saturation compared with those in low disease activity or remission (p < 0.05). DAS28 showed a moderate positive correlation with RDW-CV (r = 0.409, p < 0.001) and a weak positive correlation with RDW-SD (r = 0.301, p = 0.002). RDW-CV demonstrated better discriminative ability (AUC 0.700; 95% CI 0.595–0.806) than RDW-SD (AUC 0.624; 95% CI 0.510–0.738), though overall diagnostic performance was limited. Conclusions: RDW parameters were significantly associated with RA disease activity but showed limited accuracy as standalone biomarkers. RDW-CV performed slightly better than RDW-SD; however, neither measure demonstrated sufficient discriminative power for reliable clinical application.