Performance Of New Anti-Ccp Multiplexing Assay Comparing To Elisa Anti-Ccp3 Test

Background ACPA finds its place in early RA diagnosis. Improvements are made in measurement of ACPA with recently designed fluorescent-based microparticles immunoassay which allows the simultaneous detection of 4 anti-CCP autoantibody specificities: anti-HCP1, anti-HCP2, anti-VCP1 and anti-VCP2. Objectives The aim of this work is to evaluate the performance of new anti-CCP multiplexing assay comparing to anti-CCP3 ELISA test. Methods Detection and measurement of ACPA by FIDIS™ anti-CCP (Theradiag) multiplexing assay were compared to the anti-CCP3 ELISA (INOVA) in 171 [98 anti-CCP3 (+), 73 anti-CCP3 (-)] sera patients with early arthritis. Results Global concordance was about 81% between FIDIS anti-CCP and anti-CCP3 (Table 1 and Table 2) while, for each of four FIDIS citrullinated peptides, this concordance is shown on Table 2. We observed a good concordance between two tests. Otherwise, it is noteworthy that among anti-CCP3 (-) patients, 17 (23%) were FIDIS anti-CCP (+). Among them, 53% recognize 1 citrullinated peptide, 35% 2 peptides and 6% 3 or 4 peptides. Thus, the FIDIS anti-CCP test increases the sensitivity of detection of ACPA compared to anti-CCP3 that have proven good diagnostic performance. However, some specificities are not detected by the new method comparatively to anti-CCP3. Conclusions FIDIS anti-CCP multiplexing assay shows good performance comparing to anti-CCP3 and must be assessed on larger series of patients with early RA compared to control populations. References Anzilotti C, Merlini G, Pratesi F, Tommasi C, Chimenti D, Migliorini P. Antibodies to viral citrullinated peptide in rheumatoid arthritis. J Rheumatol. 2006 Apr;33(4):647-51.Pratesi F., Tommasi C., Anzilotti C., Puxeddu I., Sardano E., Di Colo G., Migliorini P. Antibodies to a new viral citrullinated peptide, VCP2: fine specificity and correlation with anti-cyclic citrullinated peptide (CCP) and anti-VCP1 antibodies. Clin. Exp. Immunol. 2011, 164, 337. Disclosure of Interest None declared DOI 10.1136/annrheumdis-2014-eular.6049