HLA-DRB1 allele carrier frequency in ACPA(+) and ACPA(−) RA patients and controls.

ACPA: anti-citrullinated peptide antibody, ACPA(+): ACPA-positive, ACPA(−): ACPA-negative, RA: rheumatoid arthritis, OR: odds ratio, CI: confidence interval, Pc: corrected P value, NS: not significant. Allele carrier frequencies are shown in parenthesis (%). Association was tested by Fisher's exact test using 2×2 contingency tables. Allele groups SE, D70, I67, S1, and DERAA were as defined in the Materials and Methods section.