HLA-DRB1 allele carrier frequency in ACPA(+) and ACPA(−) RA patients and controls stratified for the presence of SE.

ACPA: anti-citrullinated peptide antibody, ACPA(+): ACPA-positive, ACPA(−): ACPA-negative, RA: rheumatoid arthritis, SE: Shared epitope, OR: odds ratio, CI: confidence interval, Allele carrier frequencies are shown in parenthesis (%). Association was tested by Fisher's exact test using 2×2 contingency tables. SE negative: “A/A” or “A/other than SE or A” vs. “other than SE or A/other than SE or A”. SE positive: “SE/A” vs. “SE/other than A”. Allele groups SE, I67, D70, and S1 were as defined in the Materials and Methods section.