Frequency of human leukocyte antigens class II-DR alleles (HLA-DRB1) in Argentinian patients with early arthritis.

Patients with rheumatoid arthritis (RA) or undifferentiated arthritis (UA) in the CONAART database (Argentine Consortium for Early Arthritis) were assessed for genetic risk factors for RA, specifically for HLA-DRB1 alleles and the PTPN22 rs2476601 polymorphism associated with progression to RA. This is a case-control study. Blood samples were obtained to determine HLA-DRB1 genotypes by PCR-SSO Luminex and PTPN22 (rs2476601) polymorphism by allelic discrimination. A control group of individuals from the general Argentinian population were obtained from the national register of cadaveric organ donors. A total of 1859 individuals were included in this analysis: 399 patients from the CONAART database (347 patients with RA at study end and 52 patients with UA at study end, mean follow-up time 25 ± 18 months) and 1460 individuals from the general Argentinian population. Compared with the controls, the HLA-DRB1*04 and DRB1*09 alleles were more commonly detected in patients with RA diagnosis (OR (95% CI) 2.23 (1.74-2.85) and 1.89 (1.26-2.81)) respectively. Both patients with UA and the general population showed higher frequency of DRB1*07, DRB1*11 and DRB1*15 alleles than patients with RA. PTPN22 rs2476601 polymorphism frequency was higher in RA and UA vs the general population; however, this was significantly different only for RA vs control group (OR [95% CI] = 1.81 [1.10-3.02], P = 0.018. HLA-DRB1 typing and PTPN22 allelic discrimination could distinguish between patients with UA, patients with early RA, and the general population in Argentina. This is the first study of HLA-DRB1 alleles and PTPN22 polymorphism associations with progression to early RA in an Argentinian population.