Associations between acute phase reactant levels and disease activity score (DAS28) in patients with rheumatoid arthritis

Serum levels of acute phase reactants (APR) were measured in patients with rheumatoid arthritis (RA) and the correlations of these parameters with the disease activity score (DAS28) were investigated. The study included 47 patients with RA and 50 healthy controls. Laboratory tests included erythrocyte sedimentation rate (ESR), serum C-reactive protein (CRP), haptoglobin (Hp), ferritin, and plasma fibrinogen. Disease activity was assessed using the DAS28 score. The means (+/- SD) of ESR, CRP, Hp, ferritin, and fibrinogen levels were respectively 36.0 +/- 23.5 mm/hr, 2.4 +/- 1.9 mg/dl, 121.3 +/- 34.2 mg/dl, 67.7 +/- 36.2 ng/ml, and 371.2 +/- 96.0 mg/dl in the patients with RA, vs 16.4 +/- 11.3 mm/hr, 0.4 +/- 0.3 mg/dl, 104.0 +/- 35.3 mg/dl, 50.9 +/- 23 ng/ml, and 332.2 +/- 58.5 mg/dl in the controls. All of the APR levels were significantly higher in patients vs controls (p <0.001 for ESR and CRP; p <0.05 for Hp, ferritin, and fibrinogen). There were significant correlations between serum APR levels and disease activity based on DAS28 score in RA patients (for CRP, r = 0.650, p <0.01; for Hp, r = 0.331, p <0.05; for ferritin, r = 0.299, p <0.05; for fibrinogen, r = 0.373, p <0.01). This study indicates that serum CRP, among the various ARP tests, is the most useful biochemical marker for evaluating the disease activity of patients with RA.