AB1277 PREVALENCE OF THE DIFFERENT ANTI-CARBAMYLATED PROTEIN ANTIBODIES ISOFORMS IN FIRST-DEGREE RELATIVES OF PATIENTS WITH RHEUMATOID ARTHRITIS IN A LATIN POPULATION
Authors: Ana Sofía Leal Bramasco, Cesar Vidal Solis, Luis Eduardo Ramírez Monterrubio, Lorena Pérez Barbosa, David Vega Morales, Jorge Antonio Esquivel Valerio, Mario Alberto Garza Elizondo, Dionicio Ángel Galarza Delgado, Karina Itzel González Márquez
Journal: Annals of the Rheumatic Diseases (2019)

<h3>Background</h3> Rheumatoid arthritis (RA) affects approximately 1.5% of the population worldwide and 0.5-3.3% of the Mexican population<sup>1</sup>. Anti-carbamylated proteins (anti-CarP) antibodies are identified in RA patients with a prevalence up to 44%<sup>2</sup>, early arthritis, first-degree relatives (FDR) of patients with RA with a prevalence of 18%, and healthy controls with a prevalence of 4.7%. There is no evidence regarding the prevalence of the three different isoforms of anti-CarP antibodies worldwide. <h3>Objectives</h3> Establish the prevalence of the different isoforms of anti-CarP antibodies (IgA, IgM, IgG) in FDRs of patients with RA. <h3>Methods</h3> It is an observational descriptive cohort. Subjects underwent a complete physical examination, made by a certificated rheumatologist, which included clinical and serological measurements. The serological measurements included anti-citrullinated peptides antibodies (ACPA), RF, and anti-CarP detected by ELISA using carbamylated fetal calf serum, according to Shin J et al with some modifications. The cut-offs for the anti-CarP IgA isoform was &gt;125 U/mL, for the IgG isoform was &gt;90 U/mL, and for the IgM isoform was &gt;300 U/mL. The FDRs were classified as: suspicious arthralgia for progression according to Van Steenvergen criteria; undifferentiated arthritis (UA) and RA according to ACR/EULAR 2010; and soft tissue rheumatic diseases. <h3>Results</h3> A total of 144 FDRs from 99 RA patients were enrolled. The demographic characteristics are shown in Table 1. The prevalence (Table 2) for anti-CarP was 2.8% for IgA, 4.2% for IgG, whereas IgM was not detected. The serologic association was for RF/ACPA 4.48%, RF/anti-CarP 2.7%, FR 64.5%, ACPA 1.3%, ACPA/anti-CarP 0.69%, anti-CarP 3.4%, and no RF/ACPA/anti-Carp was observed. The group of suspicious arthralgia for progression had to 2 subjects positive for IgG anti-CarP, the group of UA had 1 subject positive for IgA anti-CarP, albeit no anti-CarP for the RA group was present. Soft tissue rheumatic diseases group had 5 subjects positive for IgG anti-CarP, while the asymptomatic group had 2 subjects positive for IgA anti-CarP. <h3>Conclusion</h3> Even though we used the 3 isoforms of anti-CarP antibodies, the prevalence of these antibodies in our cohort showed less positivity than other cohorts, who only detected the IgG isoform, worldwide. <h3>References</h3> [1] Ingris Pelaez-Ballestas, et al. Epidemiology of the Rheumatic Diseases in Mexico. A Study of 5 Regions Based on the COPCORD Methodology. J Rheumatol 2011; 38 Suppl 86:3–6. [2] Jing Shi, et al. The specificity of anti-carbamylated protein antibodies for rheumatoid arthritis in a setting of early arthritis. Arthritis Research &amp; Therapy (2015) 17:339. <h3>Disclosure of Interests</h3> None declared