Diagnostic and predictive value of anti-cyclic citrullinated peptide antibodies in patients with rheumatoid arthritis

Abstract

ABSTRACT Background: The early diagnosis and effective treatment of rheumatoid arthritis (RA) can improve the clinical outcome of the disease. However, the diagnosis of RA can be difficult and requires time. Rheumatoid factor (RF) is commonly used for the diagnosis of rheumatoid arthritis (RA). RF positivity is nonspecific for RA because it can be detected in 3-5% of nomial individuals. Recently, anti-Cyclic-Citrullinated protein antibodies (Anti-CCP) is found to be more specific to RA arthritis although in the early stages when the arthritis is undifferentiated. Objectives: The objectives of this study were to determine the sensitivity and specificity of anti- cyclic citrullinated peptide antibodies in RA patients attending rheumatology clinic in Ribat university hospital (greater Khartoum), Sudan. The criteria of the American College of rheumatology (ACR) was used as a gold standard and to compare the sensitivity and specificity of anti-CCP and RF. Moreover, to detennine the predictive value of Anti-CCP antibodies as compared to that of RF in apparently healthy individuals belonging to families with history of RA. Methodology: This was a case control study which conducted from January 2012 to March 2014. Serum samples were collected from 56 patients (n=56) and 56 matched healthy volunteers with no previous history of any type of arthritis was tested as controls. (n=56)Samples were also collected from apparently healthy relatives of patients with rheumatoid arthritis. Serum from each subject was tested for anti-CCP antibodies and by enzyme linked immunosorbent assay

(ELISA) and RF (IgM) latex test. Sensitivity and specificity of the test were evaluated using the clinical diagnosis as the gold standard. Results: The sensitivity of anti-CCP was 60.7% with 96.4% of specificity. For RF the sensitivity was 73.2% and specificity was 78.6%. The positive predictive value for anti-CCP was 94.4% (Cl: 81.3% to 99.3%) whereas for RF was 77.4% (CI: 63.8% to 87.7%). The sensitivity and specificity of anti-CCP antibodies and RF was significantly difierent (P-value < 0.001). Conclusions: Anti-CCP antibody has a higher diagnostic specificity and positive predictive value than rheumatoid factor; however sensitivity was lower than rheumatoid factor. Keywords: Anti-CCP antibodies, Diagnostic value, Predictive value, Rheumatoid arthritis; Rheumatoid factor.