Are global definitions enough? Revisiting CDAI and SDAI remission cut-offs in Brazilian rheumatoid arthritis patients

Abstract

Background Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease in which achieving remission is the most effective strategy to prevent progression and optimize long-term outcomes. The performance of commonly used disease activity indices has not been well validated in the Brazilian RA population. This study aimed to evaluate the agreement between CDAI/SDAI and the revised Boolean 2.0 remission criteria, which served as the reference standard, and to identify the most accurate CDAI and SDAI remission cut-offs in this population. Methods We conducted a cross-sectional analysis of baseline data from a Brazilian Cohort study, which included 840 patients from 11 public hospitals in Brazil. Disease activity was assessed using DAS28-CRP, DAS28-ESR, SDAI, CDAI, and Boolean 1.0/2.0. Agreement was assessed using Cohen’s kappa, and optimal remission cut-offs were determined through ROC curve analysis. Results The study population was predominantly female (89.8%), with a mean age of 57 years and a median disease duration of 12 years. DAS28-CRP showed the highest remission rate (39.2%), whereas Boolean 1.0 showed the lowest (15.1%). Strong agreement was found between Boolean 2.0, and both the SDAI (κ = 0.775) and CDAI (κ = 0.692). ROC analysis revealed that the most accurate remission cut-offs were SDAI ≤ 4.3 and CDAI ≤ 3.9, which increased remission detection by 5.9% and 6.2%, respectively. Conclusion In our cohort, SDAI ≤ 4.3 and CDAI ≤ 3.9 were the values most closely aligned with Boolean 2.0 remission. These adjusted cut-offs may help minimize overtreatment in resource-limited settings. Prospective studies assessing function, radiographic progression, and quality of life are warranted to confirm their validity in the Brazilian population.