The Disease Activity Score based on 28 joints (DAS28) has been widely used in clinical practice and research studies of rheumatoid arthritis (RA). The objective of this study was to evaluate the discordance in the DAS28 based on the erythrocyte sedimentation rate (ESR) versus C-reactive protein (CRP) levels in Korean patients with RA.
From August to December 2011, 540 patients with RA who visited two rheumatology clinics affiliated with Hallym University (Korea) and had at least one DAS28 evaluation were examined.
The mean age of the included patients was 53 years, and 82% were female. The mean duration of disease was 32.9 ± 41.2 months. The mean DAS28-ESR was higher than the DAS28-CRP (3.65 vs. 3.44; P < 0.001). In the DAS28-ESR group, 126 patients (23.3%) satisfied the criteria for remission versus 134 (24.8%) in the DAS28-CRP group. High disease activity was determined in 80 (14.8%) patients in the DAS28-ESR group and in 43 (8.0%) in the DAS28-CRP group. A comparison of the two groups with respect to four DAS28 disease activity categories showed agreement in 344 patients (63.7%; κ = 0.45). In classifying patients as European League Against Rheumatism (EULAR) responders, agreement between the two methods was shown in 56 patients (71.8%; κ = 0.76). When disagreements between the two scores occurred, more patients had a better EULAR response based on the DAS28-ESR than on the DAS28-CRP (19.2% vs. 8.9%, respectively).
The discordance between the ESR-based and CRP-based DAS28 could affect clinical treatment decisions for patients with RA.