Evaluating the efficacy of anti-cyclic citrullinated peptide antibody in the diagnosis of rheumatoid arthritis disease

Background: Rheumatoid arthritis is one of the most common autoimmune diseases. Early diagnosis can prevent side effects and disability. Anti-cyclic citrullinated peptide antibody is a specific marker to diagnose rheumatoid arthritis. This study was carried out to evaluate the efficacy of anti-cyclic citrullinated peptide in comparison with rheumatoid factor in rheumatoid arthritis patients referred to Behshti Hospital of Kashan city during 2006-7. Materials and Methods: This diagnostic value study was done on 98 randomly selected rheumatoid arthritis patients and 75 patients with other rheumatic diseases. In this study rheumatoid factor titer>35 IU/ml and anti-cyclic citrullinated peptide>6.25 IU/ml were considered positive. Results: Anti-cyclic citrullinated peptide compared to rheumatoid factor had a higher sensitivity (73.5 vs. 69.4), specificity (88 vs. 84), positive predictive value (88.9 vs. 85), and negative predictive value (71.7 vs. 67.7) for rheumatoid arthritis. The use of rheumatoid factor and anti-cyclic citrullinated peptide test together increased the specificity and positive predictive value for diagnosis of rheumatoid arthritis to 93.3 and 92.4, respectively. The mean anti-cyclic citrullinated peptide showed a significant difference in Rheumatoid arthritis (46.8 IU/ml( in comparison to non rheumatoid arthritis patients (5.3 IU/ml).Conclusion: Anti-cyclic citrullinated peptide had a better diagnostic value when compared to rheumatoid factor for detection of rheumatoid arthritis. Also combined use of rheumatoid factor and anti-cyclic citrullinated peptide had a higher specificity and positive predictive value than each alone for the diagnosis of rheumatoid arthritis.