Of the 16 possible HLA-DRB1 amino acid haplotypes at positions 11, 13, 71, and 74 [17], we observed only 10, 12, and 12 haplotypes, respectively, in Malay, Chinese, and Indian ethnic groups to be associated with ACPA-positive RA (Table 4). Here, HLA-DRB1 is linked to rheumatoid arthritis.