HLA-DRB1 and rheumatoid arthritis: Looking at the HLA-DRB1* alleles, patients with different HLA-DRB1* alleles showed an increase in anti-CCP levels that was mostly comparable to the average of the RA cohort, with the exception of patients with the HLA-DRB1*04 allele, who showed a more than 3-fold increase in anti-CCP levels above the average of the RA cohort, albeit with borderline statistical significance (χ2 = 3.74; P = 0.053).