Diagnostic value of anti-cyclic citrullinated peptide antibodies in northern Chinese Han patients with rheumatoid arthritis and its correlation with disease activity

This study was to evaluate the diagnostic value of anti-cyclic citrullinated peptide (CCP) antibodies in northern Chinese Han patients with rheumatoid arthritis (RA) and its correlation with disease activity. Clinical data and serum samples were collected from 112 RA patients and 55 non-RA patients. Statistical analyses of the correlations among anti-CCP antibodies, other serological markers, and the RA patients' clinical characteristics were performed using SPSS 11.5 software. Anti-CCP antibodies were detected in 77.7% of all RA patients and 80.4% of the RA patients with a disease duration of 3 years or less. The combined diagnosis using high titer anti-CCP antibodies (a parts per thousand yen100 RU/ml) with a concomitant positive rheumatoid factor (RF) test exhibited the greatest diagnostic specificity; it achieved 87.9% for all RA patients and 90.1% for the patients with disease duration of three years or less. Moreover, anti-CCP antibodies showed medium correlations to the RA patient's serum RF titer (r = 0.560, P < 0.001) and disease activity (DAS28 score; r = 0.404, P < 0.001). Compared with the patients with low anti-CCP antibody titers (< 100 RU/ml), patients with high anti-CCP antibody titers showed higher RF titers, worse DAS28 scores, and severe morning stiffness (P < 0.01). This study suggests that anti-CCP antibodies can be used for RA diagnosis and disease activity evaluation for northern Han Chinese patients. A combined diagnosis using both high titers of anti-CCP antibodies (a parts per thousand yen100 RU/ml) and a positive RF test markedly improves RA diagnostic specificity. Patients' DAS28 scores rise and morning stiffness intensifies with increasing anti-CCP antibody titers.