Background/Purpose:

Rheumatoid arthritis (RA) disease activity and treatment response are usually assessed by using Disease Activity Score 28-joint count (DAS28), which can be calculated using erythrocyte sedimentation rate (ESR) or C reactive protein (CRP). It has been shown that DAS28-CRP values are lower than corresponding DAS28-ESR values, especially when assessing high disease activity. However, existing guidelines do not specify how cut-offs for high disease activity differ between these two calculations. Most existing studies that compare DAS28-CRP and DAS28-ESR are drawn largely on data from clinical trials or registries. Due to potential variation between laboratories and clinical assessment at separate institutions, existing data must be validated by and compared to data from single institutions. The relationship between high disease activity cut-offs for DAS28-ESR and DAS28-CRP must be carefully characterized in order to adequately assess clinical trial data. The purpose of our study was to compare the DAS28-ESR and DAS28-CRP values from a single institution.  

Methods: We conducted a chart review for new diagnoses of RA (ICD-9 714) from January 1, 2005 to September 1, 2018 at Trinity Health in Minot, ND. Patients were excluded if they (i) had received previous treatment with a DMARD, (ii) were currently receiving treatment with steroids upon referral, or (iii) did not contain the data necessary to calculate both ESR and CRP disease activity scores. Disease severity was calculated using the Disease Activity Scores DAS28-ESR and DAS28-CRP; these values were compared with t-test. P-values were two-sided, and p-value < 0.05 was considered significant. 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’s Index was used to calculate the DAS28-CRP high disease activity cut off estimation that corresponds to DAS28-ESR of > 5.1.

Results: A total of 171 newly diagnosed RA patients met inclusion criteria.  The mean DAS28-ESR of patients on presentation was 5.061 (SD = 1.15). The mean DAS-28 CRP was 4.134 (SD = .99). The difference between mean DAS28-ESR and DAS28-CRP was statistically significant (p < .001). The prevalence of patients who met high disease activity criteria ( > 5.1) for DAS28-ESR was 48.5% and for DAS28-CRP was 14.6%. Discordance between these two parameters was 33.9%. Kappa coefficient was .307, which corresponds to a minimal level of agreement. Receiver Operator Curve and Youden’s index analysis suggested that the cut off point for high disease activity of DAS28-CRP > 4.06, which corresponds to DAS28-ESR > 5.1.

Conclusion: There is a significant difference between DAS28-ESR and DAS28-CRP, especially when assessing high disease activity of RA, even if they are performed and calculated at a single institution.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/das28-crp-cut-offs-for-high-disease-activity-assessment-is-lower-than-das28-esr-in-rheumatoid-arthritis/