LAUSR

Rheumatoid arthritis (RA) affects approximately 1.5% of the population worldwide and 0.5–3.3% of the Mexican population. The presence of rheumatoid factor (RF), anti‐citrullinated protein antibodies (ACPA) and anti‐carbamylated protein (anti‐CarP) antibodies has been described in populations at risk of RA development, such as first‐degree relatives (FDR). Anti‐CarP antibodies are present in RA patients (44%), FDR of RA patients (18%) and healthy controls (4.7%). Anti‐CarP antibodies have not been described in FDR of the Mexican population. The objective of this study was to determine the prevalence of Rheumatoid Factors (RF) isotypes, ACPA and anti‐CarP antibodies isotypes in FDR of RA patients. An observational, cross‐sectional study, in an FDR of RA cohort, was performed. We measured IgA, IgG and IgM isotypes of RF, ACPA and anti‐CarP antibodies. A total of 144 FDRs from 99 RA patients were enrolled. The prevalence of anti‐CarP antibodies 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. We found a low prevalence of anti‐CarP antibodies in our cohort of FDR of RA patients, but the prevalence of ACPA and RF were higher than other cohorts previously reported.