There was a dose-dependent effect of SE-encoding HLA-DRB1 alleles: 29.8% of RA cases and 24.9% of controls had one allele (OR 1.89, 95% CI 1.13 to 3.13), whereas 14% of RA cases and 5.6% of controls were homozygous for SE-encoding HLA-DRB1 alleles (OR 3.97, 95% CI 1.93 to 8.16) (Table 3). Here, HLA-DRB1 is linked to rheumatoid arthritis.