Antibodies to cyclic citrullinated peptide in patients with chronic arthritis attending an arthritis-monitoring clinic.

BACKGROUND Early diagnosis of rheumatoid arthritis allows prompt initiation of antirheumatic therapy, which is associated with improved outcome. The use of IgM rheumatoid factor, the most widely used serologic test in assisting the diagnosis of rheumatoid arthritis, is limited by low specificity. An enzyme-linked immunosorbent assay test detecting antibodies to cyclic citrullinated peptide (CCP) has been developed with apparently higher specificity for rheumatoid arthritis. AIM We aimed to evaluate an assay for anti-CCP antibodies by determining the prevalence and titer of antibodies to CCP in a group of patients with chronic arthritis. METHOD Thirty-four sera were collected from outpatients attending an arthritis-monitoring clinic and tested for anti-CCP and IgM rheumatoid factor. RESULTS Anti-CCP and rheumatoid factor were detected in 86% and 72% of patients with rheumatoid arthritis, respectively. Six patients negative for rheumatoid factor were positive for anti-CCP. CONCLUSION Anti-CCP antibodies are frequently detectable in high titer in patients with longstanding rheumatoid arthritis. This assay may be especially helpful in such cases when positive in rheumatoid factor-negative patients.