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Table 3 Associations of composite risk factors with ACPA positivity in patients with rheumatoid arthritisa

From: Anticitrullinated protein antibody (ACPA) in rheumatoid arthritis: influence of an interaction between HLA-DRB1 shared epitope and a deletion polymorphism in glutathione s-transferasein a cross-sectional study

  VARA (n= 703) SONORA (n= 610)
  ACPA+ (%) OR (95% CI) Pvalue ACPA+ (%) OR (95% CI) Pvalue
GSTM1/SEa,b       
   Present/Negative 50 Ref. - 59 Ref. -
   Null/Negative 56 1.26 (0.68 to 2.33) 0.456 48 0.63 (0.35 to 1.15) 0.135
   Present/Positive 79 3.65 (2.09 to 6.40) < 0.001 72 1.79 (1.05 to 3.03) 0.032
   Null/Positive 88 7.30 (4.01 to 13.29) < 0.001 77 2.29 (1.34 to 3.90) 0.002
  AP = 0.46 (0.20 to 0.73) AP = 0.38 (0.00 to 0.76)
  Padd < 0.001 Padd = 0.050
  Pmult = 0.246 Pmult = 0.063
GSTM1/Smokinga       
   Present/Never 67 Ref. - 72 Ref. -
   Present/Ever 75 1.42 (0.80 to 2.52) 0.227 67 0.72 (0.42 to 1.22) 0.223
   Null/Never 72 1.35 (0.65 to 2.79) 0.421 67 0.75 (0.42 to 1.36) 0.349
   Null/Ever 81 2.01 (1.13 to 3.55) 0.017 70 0.83 (0.49 to 1.42) 0.502
  AP = 0.12 (-1.41 to 1.65) AP = 0.44 (-0.28 to 1.15)
  Padd = 0.881 Padd = 0.231
  Pmult = 0.917 Pmult = 0.245
SE/Smokinga       
Negative/Never 55 Ref. - 58 Ref. -
Negative/Ever 53 0.90 (0.40 to 1.99) 0.788 51 0.73 (0.39 to 1.37) 0.329
Positive/Never 73 2.24 (0.97 to 5.16) 0.058 74 2.03 (1.08 to 3.82) 0.027
Positive/Ever 87 5.05 (2.31 to 11.05) < 0.001 75 2.10 (1.17 to 3.78) 0.013
  AP = 0.58 (0.31 to 0.85) AP = 0.16 (-0.34 to 0.66)
  Padd < 0.001 Padd = 0.530
  Pmult = 0.054 Pmult = 0.380
  1. aACPA, anticitrullinated protein antibody; AP, attributable proportion; GSTM1, glutathione S-transferase Mu-1; SE, shared epitope; SONORA, Study of New-Onset Rheumatoid Arthritis; VARA, Veterans Affairs Rheumatoid Arthritis. All analyses are age- and gender-adjusted. bCorresponding ORs and 95% for GSTM1/SE composite risk after further adjustment for ever smoking in VARA: Null/Negative OR = 1.22 (0.66 to 2.27); Present/Positive OR = 3.75 (2.13 to 6.59); Null/Positive OR = 7.34 (4.02 to 13.34); in SONORA, Null/Negative OR = 0.65 (0.36 to 1.18); Present/Positive OR = 1.80 (1.06 to 3.06); Null/Positive OR = 2.31 (1.36 to 3.95). "Ref." = referent group in each analysis.