DAS28‐CRP Cutoffs for High Disease Activity and Remission Are Lower Than DAS28‐ESR in Rheumatoid Arthritis

OBJECTIVE: Guidelines do not specify how cutoffs for high disease activity differ between the Disease Activity Score 28-joint count indices DAS28-erythrocyte sedimentation rate (ESR) and DAS28-C-reactive protein (CRP). Studies that compare DAS28-CRP and DAS28-ESR depend on data from clinical trials, registries, or practices with multiple providers. Existing studies use data from patients who received immunosuppressive therapy. This study compared the DAS28-ESR and DAS28-CRP values from immunosuppressive treatment-naïve patients in a single physician practice. METHODS: A retrospective electronic medical chart review was conducted for new diagnoses of rheumatoid arthritis (RA; International Classification of Diseases [ICD]-9 714), based on the American College of Rheumatology/European League against Rheumatology 2010 RA classification criteria. The number of patients with high disease activity (>5.1) was compared using ESR and CRP data to calculate the proportion of discordance. A receiver operator curve and Youden index was used to calculate the DAS28-CRP high disease activity cutoff estimation that corresponds with DAS28-ESR of more than 5.1. RESULTS: There were 171 patients included in this study. The baseline mean DAS28-ESR was higher than the baseline mean DAS-28 CRP: 5.1 ± 1.2 versus 4.1 ± 1.0 (P < 0.001); 48.5% of patients met criteria for high disease activity (score >5.1) compared with only 14.6% when measured by DAS28-CRP. Discordance was 33.9%. κ coefficient was only .307. Receiver operator curve and Youden index analysis suggested that the cutoff point for high disease activity of DAS28-CRP greater than 4.1, which corresponds to DAS28-ESR greater than 5.1. Similarly, DAS28-ESR posttreatment scores were significantly higher than DAS28-CRP. When measured by DAS28-ESR, patients in remission had higher scores as measured by DAS28-ESR (1.81) than DAS28-CRP (1.45). CONCLUSION: There is a difference between DAS28-ESR and DAS28-CRP, even when calculated for immunosuppressive treatment-naïve patients. DAS28-CRP is significantly lower than DAS28-ESR.