HLA-DRB1 and rheumatoid arthritis: The effect sizes for each of the HLA-DRB1 alleles were similar with the reported results, except most of the HLA-DRB1 alleles associated with risk of ACPA-positive RA in our study (DRB1*04:01, *07:01, *08:01, *09:01 and *10:01).