BackgroundRheumatoid arthritis (RA) affects approximately 1.5% of the population worldwide and 0.5-3.3% of the Mexican population1. Anti-carbamylated proteins (anti-CarP) antibodies are identified in RA patients with a prevalence up to 44%2, 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.ObjectivesEstablish the prevalence of the different isoforms of anti-CarP antibodies (IgA, IgM, IgG) in FDRs of patients with RA.MethodsIt 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 >125 U/mL, for the IgG isoform was >90 U/mL, and for the IgM isoform was >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.ResultsA 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.
Table 1
Population, n (%)144 (100%)Age (years), median (IQR)45.25 (18-76)Weight (kg), median (IQR)70 (42-117)Height (meters), median (IQR)1.61 (1.44-1.88)BMI, median (IQR)26.19 (16.7-47.3)Female, n (%)119 (82%)HAQ, median (IQR)0.29 (0-2.15)IQR: interquartile range, Kg: kilograms; BMI: body mass index, HAQ: Health Assesment QuestionareAbstract AB1277 Table 2POSITIVE, n (%)MIN/MAXMEDIANCRP, mg/dL19 (13%)0.0-2.270.36ESR, mm/H; mean (SD)37 (25.3%)1-7213.0 (11.95)Anti-CarP, U/mLIgA4 (2.8%)0.0-8182.0IgM0 (0.0%)0.0-565.45IgG6 (4.2%)0.0-1878.0Rheumatoid Factor, U/mLIgA31 (21.5%)1-2196.96IgM64 (44.4%)1-20515IgG14 (9.7%)1-1603.04ACPA-IgG, U/mL10 (7%)1-2001.21CRP: C Reactive Protein; ESR: erythrocyte Sedimentation Rato; anti-CarP: Anti-Carbamylated Protein; SD: Standard Deviation; ACPA: anti-Citrullinated Peptides Antibodies.ConclusionEven though we used the 3 isoforms of anti-CarP antibodies, the prevalence of these antibodies in our cohort showed less positi...
