Table 1

Description of studied populations

StudyNumber of individualsFemale:male ratioFrequency of HLA-DRB1 SE allelesrs4507692
MAF and nominal p value of association*
Number of SNPs in GWAS Number of SNPs in GWAS after
 imputation
EIRA0.45MAF=0.45
P=0.57
282 5274 756 851
 Cases 11512.4:10.59
 Controls10792.6:10.30
NARAC0.43MAF=0.43
P=0.67
398 5519 032 420
 Cases 8672.8:10.68
 Controls11942.5:10.26
  • *The rs4507692 SNP (chromosome 7) was used as a negative control instead of HLA-DRB1 SE alleles, since the rs4507692 SNP is not associated with RA but has the same minor allele frequency (MAF) as the HLA-DRB1 SE alleles.

  • †After removing the extended major histocompatibility (MHC) region.

  • ‡Patients with anti-citrullinated protein antibody positive rheumatoid arthritis (ACPA-positive RA).

  • EIRA, epidemiological investigation of rheumatoid arthritis; GWAS, genome-wide association study; NARAC, North American rheumatoid arthritis consortium; RA, rheumatoid arthritis; SE, shared epitope; SNP, single nucleotide polymorphism.