Table 3.
Associations of composite risk factors with ACPA positivity in patients with rheumatoid arthritisa
| VARA (n = 703) | SONORA (n = 610) | |||||
|---|---|---|---|---|---|---|
| ACPA+ (%) |
OR (95% CI) | P value | ACPA+ (%) |
OR (95% CI) | P value | |
| 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 | |||||
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.