Abstract
OBJECTIVES: To compare the diagnostic performance and prognostic value of the anti-cyclic citrullinated peptide (CCP1) and anti-CCP2 autoantibody tests in a clinical setting. METHODS: Anti-CCP1 and anti-CCP2 antibody tests were performed on the same serum samples obtained from 467 patients with early arthritis from the Leiden Arthritis Cohort. The sensitivity, specificity, positive predictive value, and negative predictive value for discriminating between rheumatoid arthritis (RA) and non-RA at 1 year's follow up were calculated for both tests. Results were graphically presented using receiver operating characteristic curves. Progression of radiological joint damage was assessed over 4 years in patients with RA and used to assess the prognostics values of the CCP tests. RESULTS: At a similar specificity the CCP2 test had a higher sensitivity than the CCP1 test. Both tests identified a subgroup of patients with RA with an increased rate of joint damage progression. The anti-CCP2 test identified more patients with an increased rate of joint damage progression than the anti-CCP1 test, and in multiple regression analysis CCP2 was the better predictor of joint damage. CONCLUSIONS: The CCP2 test had better diagnostic and prognostic ability than the CCP1 test.