TY - JOUR T1 - Anti-cyclic citrullinated peptide positivity in non-rheumatoid arthritis disease samples: citrulline-dependent or not? JF - Annals of the Rheumatic Diseases JO - Ann Rheum Dis SP - 511 LP - 516 DO - 10.1136/ard.2006.058933 VL - 66 IS - 4 AU - A Vannini AU - K Cheung AU - M Fusconi AU - J Stammen-Vogelzangs AU - J P H Drenth AU - A C Dall’Aglio AU - F B Bianchi AU - L E Bakker-Jonges AU - W J van Venrooij AU - G J M Pruijn AU - A J W Zendman Y1 - 2007/04/01 UR - http://ard.bmj.com/content/66/4/511.abstract N2 - Background: Antibodies directed against citrullinated proteins (eg anti-cyclic citrullinated peptide (CCP)) have excellent diagnostic and good prognostic potential for rheumatoid arthritis. Type 1 autoimmune hepatitis (AIH-1) is a chronic liver disease characterised by a variety of serum autoantibodies. Recently, in a large group of patients with AIH-1 without clear rheumatoid arthritis overlap, a relatively high percentage (9%) of anti-CCP2 positivity was scored. Objectives: To characterise the citrulline-dependence of the observed anti-CCP2 positivity in AIH-1 sera as well as in other groups of patients without rheumatoid arthritis (mainly rheumatic diseases). Methods: Serum samples of 57 patients with AIH-1 and 66 patients without rheumatoid arthritis, most of them reported as anti-CCP positive, were tested for citrulline-specific reactivity with a second generation anti-CCP kit, with the citrullinated and the corresponding non-citrullinated (arginine-containing) antigen. A subset of AIH-1 sera was also tested with a CCP1 ELISA (and arginine control). Results: The anti-CCP2 reactivity of most non-rheumatoid arthritis rheumatic diseases samples (87–93%) was citrulline-specific, whereas a relatively high percentage of AIH-1 samples (42–50%) turned out to be reactive in a citrulline-independent manner. The use of citrullinated and non-citrullinated CCP1 peptides confirmed a high occurrence of citrulline-independent reactivity in AIH-1 samples. Conclusions: In rheumatoid arthritis and most non-rheumatoid arthritis rheumatologic disease sera, anti-CCP positivity is citrulline-dependent. However in some patients, particularly patients with AIH-1, citrulline-independent reactivity in the anti-CCP2 test can occur. A positive CCP test in a non-rheumatic disease (eg liver disease) should therefore be interpreted with care, and preferably followed by a control ELISA with a non-citrullinated antigen. ER -