Reliability of Anti-Cyclic Citrullinated Peptide Antibodies (Anti-CCP) for the Diagnosis of Rheumatoid Arthritis as Compared to that of Rheumatoid Factor test

Background: Rheumatoid factor (RF) is commonly used for diagnosis of rheumatoid arthritis (RA). RF positivity is nonspecific for diagnosis of RA because it can be detected in 3-5% of normal individuals. Recent studies indicated that anti-Cyclic-Citrullinated protein (Anti-CCP) antibodies are more specific to diagnose rheumatoid arthritis and have the capacity to diagnose RA in early stages of the disease, or even before the onset of the disease when the arthritis is undifferentiated. Objectives: This study has been conducted to assess the reliability and specificity of anti-CCP in Sudanese as an indicator of RA. Patients and methods: In this study, patients were diagnosed as RA patients according to the American College of Rheumatology (ACR) criteria. To get further insight on the sensitivity and specificity of Anti-CCP test as compared to that of RF test in the diagnosis of RA, analysis of samples obtained was performed using enzyme linked immune sorbent assay (ELISA) and latex agglutination test. All the results were analyzed using Statistical Packages of Social Sciences (SPSS). Results and discussion: Anti-CCP test achieved higher specificity (86.7% Vs 60%) and sensitivity (74.3% Vs 60%) compared with RF. However, despite that the accuracy of anti-CCP to diagnose RA was high (76.5%), the false negative rate reached 21.2%. Although anti-CCP test is more accurate compared with RF; it may sometimes fail to diagnose some patients with rheumatoid arthritis. However, studies on the predictive values and other conditional ratios for anti-CCP antibodies were scarce.