LAUSR

Background: Anti-carbamylated protein antibodies (anti-CarP) have been described not only in Rheumatoid arthritis but in other systemic autoimmune diseases. Recently, they have been reported in different cohorts of Systemic Lupus Erythematosus (SLE) with a prevalence of 9-28% (1-4). Anti-CarP have been proposed as a marker of erosive arthitis in SLE(4). Objectives: The aim of this work was to assess the prevalence of anti-CarP in SLE patients from a single center cohort and their association to clinical and laboratory data. Methods: Anti-CarP were evaluated using a home-made ELISA (5), with some modifications: all the incubations has been reduced to 1.5 hrs at room temperature and the reaction was developed with diethanolamine and read at 405nm.The cut-off value of 0.350 optical density (OD) was set up, testing 230 healthy controls sera, calculating the average plus 3 times standard deviation. The ROC curve analysis demonstrated a specificity and sensitivity of 0,98 and 0,32, respectively. The OD was converted to arbitrary units (AU) with 20 AU as cut-off value. Clinical data were obtained from clinical charts. Results: Anti-CarP antibodies were found in 80/282 (28,3%) SLE patients. Complete clinical and serological data were available for 217 patients (76,9%): 71 positive and 146 negative. No clinical associations were found with anti-CarP antibodies. However, cytopenia and renal involvement were more frequently assessed in patients without anti-CarP antibodies (p: 0,019; OR 0,49; 95%CI 0,26-0,91 and p: 0,07, respectively). Among the patients evaluated, 56 were treated with anti-Blys therapy (belimumab). In this subgroup, sera collected at the first administration (T0), after 6 months (T6) and after 12 months (T12) were tested. At baseline anti-CarP were positive in 10 (17,8%) with a mean titre of 37 AU (SD: 17,9). AntiCarp titre significantly decreased at T6 (p: 0.006) and T12 (p. 0.01). Negative seroconversion was observed in 7/10 sera. Conclusion: the prevalence of anti-CarP antibodies found in our cohort is in line with to what previously reported. In our hands, anti-CarP antibodies are not associated to any clinical SLE features. References [1] Ziegelasch M, et al. Arthritis Res and Ther 2016; 18: 289. [2] Nakabo S, et al. J Rheumatol 2017 Sep;44(9):1384-1388. [3] Pecani A, et al. Arthritis Res Ther 2016 Nov 25;18(1):276. [4] Ceccarelli F, et al. Arthritis Res Ther 2018 Jun 14;20(1):126. [5] Shi J, et al. Proceedings of the National Academy of Sciences of the United States of America. 2011;108(42):17372-7. Disclosure of Interests: Rajesh Kumar : None declared, Ilaria Cavazzana: None declared, Micaela Fredi: None declared, Roberta Ottaviani: None declared, Angela Tincani Consultant for: UCB, Pfizer, Abbvie, BMS, Sanofi, Roche, GSK, AlphaSigma, Lillly, Jannsen, Cellgene, Novartis, Franco Franceschini: None declared