Contribution of subjective Disease Activity Score 28 (DAS28) components to the response to treatment of rheumatoid arthritis

Abstract

We investigated the contributions made by the subjective components of the Disease Activity Score 28 (DAS28) to the treatment response of rheumatoid arthritis (RA). In addition, factors associated with poor response to treatment at 6 months, despite normalization of objective measures, were examined. A total of 426 newly diagnosed RA patients were included. The DAS28-P score (the subjective components of the DAS28 relative to the total components) was calculated as DAS28-P = 0.56 ∗ sqrt(TJC28) + 0.014 ∗ (VAS-GH) /0.56 ∗ sqrt(TJC28) + 0.28 ∗ sqrt(SJC28) + 0.7 ∗ In(erythrocyte sedimentation rate (ESR)) + 0.014 ∗ (VAS-GH). The European League Against Rheumatism (EULAR) response was assessed after 6 months of treatment. Of those who failed to attain good EULAR responses, those for whom the objective measures (the ESR, the C-reactive protein level, and swollen joints) were normalized were defined as having failed treatment because of subjective measures. The median (IQR) DAS28 score at baseline was 4.8 (4.04–5.49) and that after 6 months of treatment 3.21 (2.41–3.95). The DAS28-P score fell significantly from baseline to 6 months in good (0.43 versus 0.28, p < 0.001) and moderate responders (0.44 versus 0.4, p = 0.003), but not in non-responders (0.43 versus 0.45, p = 0.727). Younger age, a lower DAS28 score, and a lower DAS28-P score at baseline were related to a good EULAR response. Subjects who failed to respond because of subjective measures tended to have higher DAS28-P scores at baseline. We found that RA patients with high DAS28-P scores, reflecting subjective measures, were less likely to achieve good EULAR responses 6 months after treatment initiation and tended not to be classified as good responders despite normalization of objective measures.