Distribution of HLA-DR alleles among Thai patients with rheumatoid arthritis

Abstract Objective This study was performed to investigate the association between the HLA-DR series and rheumatoid arthritis (RA) in a Thai population. Methods HLA-DR subtypes were determined in 100 Thai RA patients and 99 healthy controls (HC). HLA-DR typing was performed using INNO-LiPA HLA-DRB Decoder kits (Innogenetics) and reconfirmed using MICRO SSP HLA DNA Typing kits (One Lambda) for DRB1∗ 02 and∗ 04. Results When compared with the HC, the RA patients had higher allele frequency (AF) of DRB1∗ 04:05 (15.00% vs 7.07%, p = 0.016, pc = NS, OR = 2.319, 95%CI = 1.189–4.522) and DRB1∗ 10:01 (3.00% vs 0%, p = 0.030, pc = NS), respectively. The DRB1∗ 09:01 was slightly higher in the RA patients, without statistical significance. The AF of the shared epitope (SE) alleles (HLA-DRB1∗ 01:01,∗ 04:01,∗ 04:05 and∗ 10:01) was significantly higher in the RA patients (18.50% vs 7.58%, p = 0.002, pc = 0.046, OR = 2.769, 95%CI = 1.466–5.231, 99%CI = 1.201–6.388). The AF of HLA-DRB4∗ 01 also increased significantly more in the RA patients (40.50% vs 25.76%, p = 0.002, pc = 0.002, OR = 1.962, 95%CI = 1.282–3.003, 99%CI = 1.121–3.433). The HLA-DRB3∗ 03:01 was significantly lower in the RA patients (6.00% vs 14.14%, p = 0.008, pc = 0.023, OR = 0.388, 95%CI = 0.191–0.786, 99%CI = 0.153–0.982). Conclusion In the presence of SE, the DRB1∗ 04:05 and HLA-DRB4∗ 01 were associated with RA, and the DRB3∗ 03:01 would be a protective allele against RA in a Thai population.