HLA-DRB1 and rheumatoid arthritis: As described previously, an increased frequency of HLA-DRB1 alleles encoding the SE was found in patients with RA compared with non-RA and control subjects (56.2% versus 35.5%, OR 2.33, 95% CI 1.56 to 3.5, P < 0.001 and 56.2% versus 41.6%, OR 1.8, 95% CI 1.26 to 2.56, P = 0.001, respectively).