Evaluation of disease activity indices in Korean patients with rheumatoid arthritis

Abstract

Objective: To determine whether the rheumatoid arthritis (RA) disease activity score (DAS), levels of 28-C-reactive protein (CRP), simplified disease activity index (SDAI), and clinical disease activity index (CDAI) correspond to DAS28-erythrocyte sedimentation rate (ESR) and to determine the cut-off values for these tools in terms of classifying RA disease activity into different grades in Korean patients with rheumatoid arthritis. Methods: Two hundred twenty-three patients with RA were recruited consecutively from the Hospital for Rheumatic Diseases at Hanyang University in Seoul, Korea, part of the Hanyang University Medical Center Arthritis Network (HUMAN). First, the relationships between the DAS28-ESR and DAS28-CRP, SDAI, and CDAI were analyzed. Second, the best trade-off values of DAS28-CRP, SDAI, and CDAI were derived statistically using DAS28-ESR values as a comparator for classifying patients into the following three categories of disease activity: remission, low disease activity, and high disease activity. Results: The correlation coefficients for DAS28-ESR and DAS28-CRP, SDAI, and CDAI were 0.93, 0.85, and 0.84, respectively, indicating strong linear relationships. The cut-off values of DAS28-CRP for classifying the disease activity of RA patients as remission, low disease activity, and high disease activity were 2.19, 2.60, and 4.07, respectively, and those for SDAI were 3.75, 7.50, and 16.88, respectively. For CDAI, the cut-off values for these three disease activity categories were 3.62, 7.38, and 16.50, respectively. Conclusions: DAS28-CRP, SDAI, and CDAI are valid and sensitive assessment indices of RA disease activity that are comparable to the DAS28-ESR. The cut-off values of these tools derived in this study are likely to be useful for routine monitoring of Korean RA patients and for informing the treatment of these patients.