Moreover, unlike the results of a longitudinal study, reporting higher disease activity over time in anti-CarP-positive patients [12], the findings of our cross-sectional analysis agree with the lack of association with disease activity reported by others [13]. Unlike citrullination – that is an enzimatically mediated reaction – carbamylation is a chemical reaction that occurs in the presence of a reactive metabolite (cyanate) [6]. for ACPA and three NHS were positive for RF (3.06%). Among disease controls, anti-CarP antibodies were detected in 33 patients (16.5%), ACPA in 29 patients (14.5%) and RF in 64 patients (32%). In particular, 16.8% of patients with systemic lupus erythematosus and 31.1% of patients with Sj?gren syndrome were positive for anti-CarP. Lerisetron Lerisetron The sensitivity of anti-CarP, ACPA and RF was 46.8%, 61.8% and 64.4%, respectively and specificity was 91.95%, 89.93% and 76.51%, respectively. Conclusions The present study extends the knowledge of anti-CarP antibodies, confirming previous data around the diagnostic accuracy of anti-CarP in RA in a large cohort of Italian patients. Anti-CarP antibodies exhibited relatively low sensitivity and slightly higher specificity compared to ACPA and RF. Even if predominantly present in RA, anti-CarP was detected in a variable percentage of patients with other autoimmune rheumatic diseases and their generation could be attributed to the inflammatory status; the clinical relevance of anti-CarP antibodies in these latter patients should be further decided. Keywords: Rheumatoid arthritis, Autoimmune rheumatic diseases, Systemic lupus erythematosus, Sj?gren syndrome post-translational modifications, Anti-carbamylated proteins antibodies, Anti-citrullinated peptides antibodies, Rheumatoid factor Background The discovery of autoantibodies in patients with RA facilitated the subgrouping of these patients for more accurate therapeutic management, resulting in more efficient disease control [1]. Beside the well-known rheumatoid factor (RF), anti-citrullinated protein antibodies (ACPA) have been reported to be a very useful diagnostic and prognostic marker of RA [2]. Lerisetron ACPA have remarkable sensitivity for this disease, with high predictive value for RA development and severity [2, 3]. The importance of ACPA in RA was highlighted by the inclusion of ACPA status in the 2010 classification criteria for RA by allowing the division of patients with RA into two major subsets: ACPA-positive and ACPA-negative [4]. Although ACPA have an important role in the diagnosis of RA, there is still Igf1r a continuous demand for new biomarkers to further improve the early diagnosis of RA and especially its seronegative subgroup [5]. Recently, a new autoantibody system recognising antibodies against carbamylated proteins (anti-CarP) has been described [6] but has not yet been implemented for commercial use. Initially, Shi et al. identified homocitrulline as the main aminoacid involved in the binding of autoantibodies in seronegative patients with RA [7]. Carbamylation is usually a chemical reaction mediated by cyanate that Lerisetron modifies lysine residues [5]. Normally the level of cyanate is in equilibrium with urea but specific conditions like inflammation can warp this equilibrium through a myeloperoxidase-dependent mechanism [8, 9]. This leads to the local increase of cyanate levels, thus empowering the degree of carbamylation [10]. Although the high resemblance in structure between citrulline and homocitrulline, inhibition and cohort studies have exhibited that ACPA and anti-CarP are different and impartial antibody subsets that do not cross-react with each other [4, 5]. Unlike ACPA, the presence of anti-CarP has not been associated with HLA-shared epitope (SE) and/or smoking [11]. An interesting finding was the presence of anti-CarP in ACPA-negative patients with RA and their association with increased disease activity [12, 13] and severe joint damage [13, 14]. Moreover, anti-CarP have been detected Lerisetron in patients with arthralgia and their presence has been independently associated with the risk of developing RA [15]. In addition, anti-CarP are present in serum from patients with RA many years before the clinical appearance of the disease [14, 16, 17] and have also been identified in healthy first-degree relatives of patients with RA [18]. Recently, Shi et al. investigated the diagnostic performance of anti-CarP in RA in a large cohort of patients with early arthritis and demonstrated that these antibodies are predominantly detected in RA, but that a small percentage of patients with almost all forms of early arthritis were also anti-CarP-positive [19]. Considering the high prognostic and predictive value that anti-CarP have exhibited in patients with RA, the aim of this study was to evaluate their prevalence, sensitivity and specificity in a large monocentric cohort of patients with RA compared to other autoimmune rheumatic diseases (AIRDs). Methods Patient populations We evaluated a total of 607 frozen stored serum samples from 309 patients with established RA diagnosed according to the 2010 American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) criteria,.