The diagnostic value of anti-cyclic citrullinated peptide antibodies and rheumatoid factor in patients with rheumatoid arthritis

Objective: To identify the diagnostic value of anti-cyclic citrullinated peptide (anti-CCP) antibodies and rheumatoid factor (RF) in patients with rheumatoid arthritis (RA). Methods: Serum levels of anti-CCP antibodies were determined by enzyme-linked immunosorbent assay, and levels of RF were determined by nephelometry in 145 patients with RA and 75 patients with non-RA rheumatic diseases. Results: Among the 145 patients with RA, 119 patients (82.1%) tested positive for anti-CCP antibodies, and 116 patients (80.0%) tested positive for RF. The sensitivity, specificity, positive predictive value, and negative predictive value of anti-CCP antibodies for diagnosing RA were 82.1%, 88.0%, 93.0%, and 71.7% respectively. Those for RF were 80.0%, 62.7%, 81.1%, and 61.0% respectively. The presence of either anti-CCP antibodies or RF increased sensitivity to 88.3%, and when they both were present, the specificity increased to 94.7%. The positive rates for anti-CCP antibodies in the RF-positive RA, RFnegative RA, and non-RA patients were 93.1%, 37.9%, and 12.0% respectively. Conclusion: With its high sensitivity and specificity, the anti-CCP antibodies assay is a useful test for diagnosing RA. The use of anti-CCP antibodies and RF in combination further increases the diagnostic value for RA.