Diagnostic value of third generation anti-cyclic citrullinated peptide assay in rheumatoid factor negative rheumatoid arthritis

Objective: This study aimed to evaluate the diagnostic usefulness of second and third generation anticyclic citrullinated peptide (anti-CCP2 and anti-CCP3) assays in Chinese patients with rheumatoid arthritis (RA), and to identify the potential advantages of anti-CCP3 diagnosis in rheumatoid factor (RF) negative RA patients. Methods: Serum samples were obtained from 148 RA patients and 120 controls (72 healthy subjects and 48 patients with rheumatic diseases). The routine screening of RF was performed using RFII Tina-quant (R) Turbidimetry reagents on a turbidimetry analyzer. Furthermore, the serum levels of anti-CCP2 and anti-CCP3 were detected using special kits. The individual proportions and comparisons for diagnostic capability of anti-CCP2 with anti-CCP3 were calculated for RA and RF-negative RA. Results: No significant differences were revealed in age, sex rate and disease duration between RA patients and controls (P > 0.05). The positive rates of RF, anti-CCP2 and anti-CCP3 were all significantly higher in RA patients than those in control group (P < 0.01). Meanwhile, the sensitivity of anti-CCP2 was lower than that of anti-CCP3 (77.7% vs 81.1%), whereas the specificity of anti-CCP2 was higher than that of anti-CCP3 (95.8% vs 92.5%). Besides, the sensitivity of anti-CCP3 was higher than anti-CCP2 (78.3% vs 71.6%) in RF-negative RA patients. Conclusion: The diagnostic performance of anti-CCP3 in RA patients was similar to anti-CCP2, while a superior specificity of anti-CCP3 was exhibited in RF negative RA patients compared with anti-CCP2.