Anti-citrullinated protein/peptide antibodies (ACPA) have recently emerged as sensitive and specific serological markers of rheumatoid arthritis (RA), providing superior alternative of the rheumatoid factor (RF) test in the laboratory diagnostics of RA. We compare the change of serum RF, CRP, IgG, IgM, IgA, total complement, C3 and C4. The sera sample was collected from 123 patients with RA. ACPA were detected with ELISA, and RF, CRP and total complement (Ct), C3 and C4 were examined by automatic biochemical analyzer. Serum RF and total complement concentrations were significantly higher in ACPA+ than in ACPA-, but there were no correlation between ACPA and RF and Ct. Between ACPA+ and ACPA-, there were no significant difference of CRP, IgG, IgM, IgA, total complement, C3 and C4. While there were significant correlation between the concentration of C3 and IgM and ACPA in ACPA+.
This is the first study to show that ACPA concentration in ACPA+ patients with RA is positively related to serum IgM and C3 levels.