Expression and diagnostic utility of anti-cyclic citrullinated peptide antibodies in juvenile idiopathic arthritis

Background: Juvenile idiopathic arthritis (JIA) is a clinically heterogeneous group of arthritis occurring in children. Anti-cyclic citrullinated peptide (anti-CCP) antibodies have been recently included in the revised diagnostic criteria for adult onset rheumatoid arthritis. Its diagnostic value in JIA is still debatable. Objective: The study is aimed to investigate the expression and diagnostic utility of anti-CCP antibodies in pediatric JIA in relationship to its various clinical phenotypes. Methods: Forty children and adolescents (13 males, 27 females) with JIA as well as 35 healthy children were enrolled in this cross-sectional study. Serum anti-CCP antibodies were determined by enzymatic immunoassay and its expression was statistically correlated to clinical, laboratory, and radiological data of the patients. Results: Anti-CCP antibodies were positive in 8 (20%) patients while not expressed in the control group. Seven out of the 8 positive cases (87.5%) had polyarticular JIA and only one patient (12.5%) had the oligoarticular onset variety. A significant positive correlation was elicited between the anti-CCP antibody levels and the number of tender joints (r= 0.39), swollen joints (0.68) and disease duration (r = 0.59). Radiographic erosive arthritis was found in 8 patients with positive anti-CCP antibodies; 7 of whom (87.5%) suffered the polyarticular subtype and only one patient (12.5%) had the oligoarticular subtype. All the rheumatoid factor (RF) seropositive patients had positive anti-CCP antibody as well as radiographic erosive arthritis. The overall anti-CCP antibody diagnostic value in our series showed a sensitivity and specificity of 20% and 100% respectively and the positive and negative predictive values were 100%, and 52.2%, respectively. Conclusion: Anti-CCP antibodies have a low sensitivity but high specificity in patients with JIA with a significant relationship to clinical and radiologic severity especially in RF seropositive cases. It may thus have a diagnostic and/or prognostic utility in severe polyarticular onset disease.