HLA-DRB1 and rheumatoid arthritis: In our study, the HLA-DRB1*01 and *04 alleles demonstrated predisposition to RA: OR = 4.7 [CI: 3.3–6.8], p = 0.0004 and OR = 3.1 [CI: 2.3–4.3], p = 0.00001, respectively.