Comparison between DAS28-ESR and DAS28- CRPus for patients with rheumatoid arthritis: application in a population of southern Brazil

Abstract

The Disease Activity Score 28 (DAS28) shows discrepancies when using erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) scores to assess rheumatoid arthritis (RA). This study aimed to verify the agreement between the DAS28-CRP and DAS28-ESR scores in patients with RA from the south of Brazil. A unicentric cross-sectional study was performed (n = 56). The diagnosis of the patients followed the American College of Rheumatology/ European League Against Rheumatism criteria, and their DAS28 were calculated. The DAS28-ESR score was higher than the DAS28-CRP (DAS28-ESR mean 4.8±1.6; DAS28-CRP mean 4.3±1.4) for 83.9% of the patients. The DAS28-CRP and DAS28-ESR scores showed a very strong correlation (Pearson's coefficient = 0.922; P<0.0001, 95% CI +0.87 to +0.95, statistical power 100%). Spearman's correlation coefficient (0.49; P=0.0001, 95% CI +0.25 to +0.67, statistical power 47.54%) showed a moderate correlation between the unique components of the DAS28 formulas. There was agreement between the tests in only 36 of the patients (64.29%). Among the discordant categories, DAS28-ESR overestimated the classification in 16 patients (28.5%). The Kappa coefficient between the categories was 0.465 (SE 0.084, 95% CI +0.301 to +0.630), showing a moderate degree of agreement between the instruments. Although the DAS28-ESR and DAS28-CRP were highly correlated, they differed significantly in terms of patient categorization and should not be used interchangeably.