Background/Purpose: Discrepancies between erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) elevations with clinical disease activity frequently occur in rheumatoid arthritis (RA) patients and may be due to comorbid factors other than RA disease activity.  We hypothesize that common comorbidities such as current or prior tobacco use, congestive heart failure (CHF), coronary artery disease (CAD), and diabetes mellitus (DM) are associated with discrepancies in inflammatory marker elevations in RA patients.

Methods: We performed a cross-sectional analysis using data collected at the baseline visit in the Veterans Affairs Rheumatoid Arthritis (VARA) cohort.  We obtained demographics and comorbidities (tobacco use, CHF, DM, CAD, sleep apnea, chronic obstructive pulmonary disease, malignancy, osteoarthritis, obesity) from linked Decision Support Services (DSS)-derived medical data. We used the following cutpoints to define normal laboratory values for ESR and CRP: 1)ESR for age over 50, 20mm/hr for men and 30 mm/hr for women; age under 50, 15mm/hr for both sexes 2) CRP of 0.8 mg/dL for both sexes. Concordant values were defined as both tests either being above or below these cutpoints.  We analyzed the frequencies of comorbidities in patients with low disease activity by the clinical disease activity index (CDAI ≤ 10) in relation to:  1) concordant vs. discordant elevations in inflammatory markers and 2) low or moderate/high disease activity by DAS28-ESR (<3.2 or ≥3.2) and DAS28-CRP (<2.67 or ≥2.67). Finally, we documented the frequencies of comorbidities in patients who met all the current ACR/EULAR Boolean-based definition requirements and in those who met only the 3 clinical criteria but failed the CRP ≤ 1 criterion.

Results: We identified 1158 RA patients with baseline ESR and CRP values.  There were 392 with concordantly normal, 368 with concordantly elevated, 205 with elevated ESR/normal CRP and 193 with elevated CRP/normal ESR at baseline.  Patients in low disease activity by the CDAI were equally likely to have an elevated CRP and normal ESR as they were to have a normal CRP and elevated ESR, irrespective of comorbidities.  Fewer than 10% of patients with a low CDAI had moderate-high disease activity by DAS28-ESR and DAS28-CRP. There were 157 patients who met all ACR/EULAR Boolean remission criteria and 35 who met all criteria except for CRP ≤1.  Among tobacco users, 20% who otherwise would have met ACR/EULAR remission criteria did not due to a CRP > 1.

Conclusion: Common medical comorbidities are frequently associated with elevated ESR and/or CRP in patients with RA.  ESR by itself or as part of the DAS28-ESR was as likely to be elevated and categorize patients in low disease activity as CRP by itself or as part of the DAS28-CRP.  Despite potential concern that the presence of various comorbidities might significantly influence ESR and CRP and decrease the likelihood that patients meet current ACR/EULAR remission criteria, we did not observe strong evidence for this problem in veterans with RA.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/discordant-inflammatory-markers-in-veterans-with-rheumatoid-arthritis-baseline-characteristics-and-relationship-with-disease-activity/