Diagnostic value and clinical significance of anti-carbamylated protein (anti-CarP) antibodies in Egyptian patients with rheumatoid arthritis

Aim of the work: The study was performed to assess the diagnostic potential of anti-carbamylated proteins (anti-CarP) antibodies in Egyptian patients with RA and their relation to clinical manifestations, laboratory findings and radiological damage. Patients and methods: The study involved 90 RA patients and 90 matched healthy controls. Disease activity score (DAS28) and health assessment questionnaire (HAQ) were assessed. Plain x-ray hands and feet were performed and assessed by modified Larsen's score. Laboratory investigations including acute phase reactants, rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) and anti-CarP antibodies were estimated. Results: The patients mean age was 42.6 +/- 10.4 years (20-60 years), disease duration was 4.3 +/- 3.3 years and were 82 females (91.1%) and 8 males (8.9%). The mean DAS28 was 4.9 +/- 1.2, HAQ was 1.6 +/- 0.7 and Larsen score 33.8 +/- 12.2. 29/90 (32.2%) patients were positive for anti-CarP antibodies and were significantly associated with extra-articular manifestations and deformity (p < 0.001), but not with acute phase reactants. Anti-CarP antibodies significantly associated with modified Larsen's (p < 0.001), but not DAS28 (p = 0.13). The sensitivity and specificity were 32.2% and 96.7% for anti-CarP antibodies, 61.1% and 97.8% for anti-CCP antibodies, 66.7% and 91.1% for RF respectively. 25.7% of anti-CCP negative patients showed anti-CarP positivity, and radiological damage was significantly associated with anti-CarP in them. Conclusion: The sensitivity of anti-CarP antibodies was low in comparison to both RF and anti-CCP; however, they showed high specificity and were detected in anti-CCP negative patients, so they could be useful to test beside anti-CCP and RF. Anti-CarP antibodies may reflect disease radiological damage. (C) 2019 Publishing services provided by Elsevier B.V.