Risk of developing RA according to HLA-DRB1 risk alleles and smoking status.
| HLA-DRB1/Smoking | No. Cases | OR (95% CI) |
|---|---|---|
| SE (*01:01, *04:01, *04:04, *04:05, *04:08, *04:10, *10:01) | ||
| −/− | 287 | reference |
| −/+ | 52 | 2.38 (1.47–3.85) |
| +/− | 1054 | 5.91 (4.86–7.19) |
| +/+ | 217 | 14.05 (8.85–22.30) |
| AP†† | 0.48 (0.26–0.70) | |
| RERI†† | 6.76 (0.84–12.67) | |
| S†† | 2.07 (1.32–3.26) | |
| *01:01 | ||
| +/− | 260 | 3.72 (2.85–4.86) |
| +/+ | 57 | 9.58 (4.85–18.95) |
| AP†† | 0.45 (0.09–0.80) | |
| *04:05 | ||
| +/− | 662 | 9.01 (7.09–11.46) |
| +/+ | 125 | 16.31 (9.03–29.46) |
| AP†† | 0.37 (0.02–0.73) | |
| *10:01 | ||
| +/− | 115 | 5.79 (3.82–8.77) |
| +/+ | 26 | 24.71 (6.76–90.29) |
| AP†† | 0.71 (0.34–1.09) | |
| *09:01 | ||
| +/− | 401 | 4.41 (3.48–5.59) |
| +/+ | 72 | 7.10 (4.06–12.41) |
| AP†† | 0.15 (−0.28–0.59)# | |
| RERI†† | 1.09 (−2.52–4.71) | |
| S†† | 1.22 (0.67–2.22) | |
† OR were calculated by comparing each group with the corresponding reference group [individuals without HLA–DRB1 risk alleles (*01:01, *04:01, *04:04, *04:05, *04:08, *04:10, *09:01, *10:01)], and were adjusted for age and sex.
↵†† The attributable proportions (AP), relative excess risk due to interaction (RERI), and synergy index (S) were calculated for gene-environmental interaction.
↵# Not statistically significant (p > 0.05). RA: rheumatoid arthritis.