When compared in pairs in terms of HLA-DRB1 alleles, R alleles were not significantly different between ACPA-negative RA patients and healthy controls (P=0.21) and P alleles were not significantly different between ACPA-positive RA patients and ACPA-negative RA patients (P=0.24) Table 1. This evidence concerns the gene HLA-DRB1 and rheumatoid arthritis.