ABSTRACT
Objective To investigate the expression of calreticulin and its correlation with autoantibodies and inflammatory cytokines in patients with early rheumatoid arthritis (RA). Methods Serum samples were obtained from 106 patients with early active RA, 95 patients with stable RA, 85 osteoarthritis (OA) and 80 healthy controls (HC). Serum levels of calreticulin, anti- cyclic peptide antibody (CCP), interleukin (IL)-1β, IL-6 and tumor necrosis factor (TNF)-α were measured by enzyme-linked immnuosorbent assay (ELISA). The serum level of rheumatoid factor (RF) was detected by immunoturbidimetry. The correlations between serum calreticulin and inflammatory cytokines were evaluated using Spearman's rank correlation test. Results Serum levels of calreticulin were significantly higher in patients with early active RA [(5.84±2.62)μg/L] than those in patients with stable RA [(4.26±1.42)μg/L], patients with OA [(3.92±1.10)μg/L] and HC [(3.86 ± 0.91)μg/L] (P<0.001). There were no statistical differences in serum levels of calreticulin between stable RA, OA and HC groups (P>0.05). Serum levels of calreticulin were significantly higher in RF-positive RA patients than those of RF-negative RA patients [(6.12±2.87)μg/L vs. (4.92±1.22)μg/L, P=0.045]. Serum calreticulin levels were also significantly higher in anti-CCP-positive RA patients than those of anti-CCP-negative RA patients [(6.39±2.93)μg/L vs. (4.69±1.17)μg/L, P=0.002]. The serum level of calreticulin was positively correlated with IL-1β (rs=0.386, P=0.009), IL-6 (rs=0.405, P=0.006) and TNF-α(rs=0.428, P=0.003) in early active RA patients. Conclusion The elevated serum level of calreticulin is related to autoantibodies and inflammatory cytokines in early RA patients, suggesting that calreticulin can be used as a potential biomarker for early diagnosis and prognosis of RA.