A strong positive association between the frequency of DRB1*04 and RA (P = 1.00×10−22, Corrected P [Pc] = 1.31×10−21, odds ratio [OR] 2.40, 95% confidence interval [CI] 2.01–2.86, Table 2) was confirmed. Here, HLA-DRB1 is linked to rheumatoid arthritis.