Table 4.
Association of smoking or HLA-DRB1 SE and anti-CPP3 IgG in patients with RA compared with controls adjusted for age and sex
| Anti-CPP3 IgG | RA patients, n (%) | Controls, n (%) | OR (95 % CI) | |
|---|---|---|---|---|
| Smokinga | ||||
| – | – | 58 (30.2) | 90 (49.7) | Ref. |
| + | – | 119 (62.0) | 85 (47.0) | 1.73 (1.10–2.72) |
| – | + | 5 (2.6) | 2 (1.1) | 4.04 (0.73–22.32) |
| + | + | 10 (5.2) | 4 (2.2) | 3.61 (1.05–12.44) |
| RERI = −1.17 (−18.21, 8.19), AP = −0.30 (−7.38, 0.46), SI = 0.71 (0.08–6.55), MI = 0.46 (0.059–3.59), p value = 0.46 | ||||
| HLA-DRB1 SEb | ||||
| – | – | 64 (33.3) | 107 (62.6)) | Ref. |
| + | – | 113 (58.9) | 59 (34.5) | 3.33 (2.11–5.23) |
| – | + | 6 (3.1) | 3 (1.8) | 3.55 (0.84–15.03) |
| + | + | 9 (4.7) | 2 (1.2) | 8.80 (1.80–43.03) |
| RERI = 1.98 (−10.10, 30.25), AP = 0.26 (−3.96, 0.57), SI =1.44 (0.18–11.19), MI = 0.70 (0.08–5.81), p value = 0.74 | ||||
aDefined as ever smoker
b HLA-DRB1 shared epitope (SE) defined as 0101/0401/0404/0405/0408
OR odds ratio, CI confidence interval, RERI relative excess due to interaction, AP attributable proportion due to interaction, SI synergy index, MI multiplicative interaction