Objective:To identify the sensitivity and specificity of the anti-cyclic citrullinated peptide antibody (anti-CCP) and rheumatoid factor (RF) in a diagnosis of Korean early rheumatoid arthritis (RA). Methods:Two hundred and sixty two patients diagnosed with RA were examined retrospectively and classified by three groups. A group 1 had a disease duration＜24 months, and group 2 had a duration＞24 months, and the third was a group of total patients. The sensitivity and specificity of the RF and anti-CCP in each group of RA were identified. Patients of the connective tissue disease other than rheumatoid arthritis were tested with RF and anti-CCP. Results: The sensitivity/specificity of RF and the anti-CCP in early RA were 90.4%/68.0% and 87.5%/89.3%, 91.3%/68.0%, 81.7%/89.3% in each, and 90.4%/68.0% and 84.7%/89.3% in the total RA patients. The accurate diagnosis rate, which is defined as (number of true positives plus true negatives)/ the total number of patients), of the RF and anti-CCP was 79.2%/88.4% in the early RA group, and 79.4% and 89.0% in the total patients group. Conclusion: Anti-CCP is more specific than RF in diagnosing RA. Although it is not statistically significant, diagnositc sensitivity of anti-CCP in early RA group is higher than that of established RA group.

Keywords: Rheumatoid arthritis, Rheumatoid factor, Anti-cyclic citrullinated peptide