The objective of the present study was to determine the efficacy of anti-cyclic citrullinated peptide (anti-CCP) antibody detection in the early diagnosis of rheumatoid arthritis (RA), as well as to compare three commercially available enzyme-linked immunosorbent assay (ELISA) kits used to detect such antibodies. We analysed the presence of anti-CCP antibodies in the sera of 78 patients who had been newly referred from primary healthcare centres to the Early Polyarthritis Unit. We also included in the study a group of 50 healthy controls. None of the patients had previously received treatment for the disease. After 1-year follow-up, the diagnosis of RA was confirmed in 53 of these patients. The ELISA kits under study were IMMUNOSCAN RA (Euro-Diagnostica AB), QUANTA Lite™ CCP IgG ELISA (INOVA Diagnostic) and DIA-STAT™ Anti-CCP (Axis-Shield Diagnostics); the sensitivity obtained was 52.8%, 58.5% and 52.8%, respectively, with 100% specificity for all three kits. Anti-CCP antibodies detected the presence of RA in 26% of patients without positive rheumatoid factor (RF). The sum of anti-CCP antibodies or the presence of RF gave a sensitivity of up to 67%, with specificity ranging between 94 and 97%. Anti-CCP antibodies show high specificity for the diagnosis of RA. The three ELISAs analysed offer the same degree of diagnostic accuracy.
Background: The high specificity of anti-cyclic citrullinated peptide antibodies (anti-CCP) helps substantially in the diagnosis of rheumatoid arthritis (RA), combined with classical markers such as rheumatoid factor (RF). The recent introduction of third-generation methods (anti-CCP3) for anti-CCP detection could further improve diagnostic efficiency. The aim of this study was to determinate the diagnostic efficiency (sensitivity and specificity) of anti-CCP using a new anti-CCP3 method and to compare it with the previous second-generation method (anti-CCP2).
Methods: Anti-CCP were studied in sera of 234 patients with recent-onset polyarthritis (ROP) (age ≥16 years; evolution time ≥4 weeks ≤1 year; 2 or more inflamed joints, without drug therapy). After 1 year, 124 patients were diagnosed with RA (American College of Rheumatology criteria). Two ELISAs, an anti-CCP2 and an anti-CCP3, were performed.
Results: The best sensitivity according to receiver operating characteristic curves was 51.5% and 54.8% for anti-CCP3 and anti-CCP2, with a specificity of 96.2% and 98.1%, respectively (optimal cutoffs 14.2 and 18.7 U/mL). Significant correlations were obtained (p<0.001) when the methods were compared to each other and to RF.
Conclusions: Testing with both types of anti-CCP kit is highly specific for the presence of RA. In our ROP group, anti-CCP2 and anti-CCP3 exhibited similar diagnostic efficiency.