Background The erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) are two commonly used indirect measures of the extent of inflammation in rheumatoid arthritis (RA). As current RA treatment guidelines strongly emphasize early and aggressive treatment aiming at fast remission, optimal measurement of inflammation in this patient group is becoming increasingly important (Combe et al., 2007; Smolen et al., 2010). However, although dependencies with age, gender, and body mass index have been shown for both inflammatory markers, it remains unclear which inflammatory marker is least affected by these effects in patients with early rheumatoid arthritis.
Objectives To determine which inflammatory marker, the ESR or CRP, is least affected by age, gender, and BMI in patients with early RA.
Methods Baseline data from 589 patients from the DREAM registry were used for analyses. Associations between the inflammatory markers and age, gender, and BMI were evaluated first using univariate linear regression analyses. Next, it was tested whether these associations were independent of a patient's current disease activity (as measured with the other core components of the DAS28) as well as of each other using multiple linear regression analyses with backward elimination. The strengths of the associations were compared using standardized beta (β) coefficients.
Results Both ESR and CRP were univariately associated with age, gender, and BMI, although the association with BMI disappeared in multivariate analyses. ESR and CRP concentrations significantly increased with age (β-ESR=0.017, p<0.001 and β-CRP=0.009, p=0.006), independently of the number of tender and swollen joints, patient-reported wellbeing, and gender. Furthermore, women demonstrated average ESR levels that were significantly higher than that of men (β=0.198, p=0.007), whereas men had higher CRP levels (β=-0.182, p=0.048). The effects were shown to be strongest on the ESR.
Conclusions Age and gender are independently associated with the concentrations of both acute phase reactants in early RA, emphasizing the need to take these external factors into account when interpreting disease activity measures.
Combe B, Landewe R, Lukas C, Bolosiu HD, Breedveld F, Dougados M, et al. EULAR recommendations for the management of early arthritis: report of a task force of the European Standing Committee for International Clinical Studies Including Therapeutics (ESCISIT). Ann Rheum Dis. 2007;66(1):34-45.
Smolen JS, Aletaha D, Bijlsma JW, Breedveld FC, Boumpas D, Burmester G, et al. Treating rheumatoid arthritis to target: recommendations of an international task force. Ann Rheum Dis. 2010;69(4):631-7.
Disclosure of Interest None declared
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