ANTI-CCP AND ANTI-KERATIN ANTIBODIES IN RHEUMATOID ARTHRITIS, PRIMARY SJOGREN'S SYNDROME AND WEGENER'S GRANULOMATOSIS

S. Kamali, N. Gurel Polat , E. Kasapoglu , A. Gul , L. Ocal , O. Aral , M. Konice , S. Badur , M. Inanc Dept. of Internal Medicine, Dept. of Virology and Basic Immunology, Istanbul University Istanbul Medical Faculty, Istanbul, TurkeyObjectives: Primary Sjogren's syndrome (pSS) and Wegener's granulomatosis (WG) may cause polyarthritis and rheumatoid factor (RF) positivity and additionally both diseases might coexist with rheumatoid arthritis (RA) (1). Our aim is to investigate the frequency of antibodies to cyclic citrullinated peptides (anti-CCP) and keratin (AKA) in patients with RA, pSS and WG and to determine the specificity and sensitivity of those autoantibodies for RA.Methods: We included into the study 46 patients with RA (37 females, 9 males; median age 54 years; mean disease duration 160.6 ± 90.6 months), 32 with pSS (all females; median age 50,5 years), 22 with WG (12 females, 10 males; median age 47,5 years) and 40 healthy controls. Rheumatoid factor, anti-CCP and AKA were detected by nephelometry, ELISA (EUROIMMUN) and IIF, respectively. Cutt of value for anti-CCP antibodies was 5 RU/ml. The agreement between those tests in RA were evaluated by kappa test and specificity and sensitivity of those tests for RA were calculated.Results: Among patients with pSS and WG, anti-CCP positivity was found in only one patient with pSS and AKA was not detected in patients with pSS and WG. Healthy controls were negative for all three autoantibodies. Kappa values in RA were: RF-anti-CCP: 0.25, RF-AKA: 0.02, anti-CCP-AKA: 0.13. The specificity and the sensitivity for RF were calculated as 44%-43% for RF, 98%-65% for anti-CCP and 100%-58% for AKA. In RA patients with RF positivity, AKA was positive in 44% and anti-CCP was 62%. In RA patients with negative RF, AKA was positive in 56% and anti-CCP was 38%. In patients with RA, the prevalence of positivity for the combination of RF, AKA and anti-CCP tests was: RF + anti-CCP: 34%, RF + AKA: 26%, AKA + anti-CCP: 76%. When we combined all tests for autoantibodies (RF, AKA, anti-CCP), 87% of the patients with RA had at least one positive result.Conclusion: The specificity and sensitivity of AKA and anti-CCP was found to be higher than RF in selected RA patients with low RF prevalence. High specificity of anti-CCP and AKA antibodies for RA were demonstrated for the controls having arthritis and RF positivity without diagnosis of RA.In RA, the concordance for the presence of three autoantibodies was found rather low (21%). By application of all three autoantibody tests in patients with RA, there was a considerable increase in patients with at least one positive result. We recommend that considering their specificity and sensitivity, in addition to RF, AKA or anti-CCP autoantibodies, preferentially both of them should be tested in the differential diagnosis of arthritic conditions.References: 1. Douglas G, Bird K, Flume P, Silver R, Bolster M. Wegener's granulomatosis in patients with rheumatoid arthritis. J Rheumatol 2003;30:2064-2069Citation: , volume , supplement , year 2004, page Session: Rheumatoid arthritis – Clinical aspects