Table 1. Associations of HLA-SE and smoking with presence of ACPA in patients newly presenting with CSA.
| ACPA positive, n (%) | ACPA negative, n (%) | OR (95% CI) | p-value | ||
|---|---|---|---|---|---|
| All patients | |||||
| HLA-SE | Absent | 27(39) | 259 (57) | Reference | -- |
| Present | 42 (61) | 194 (43) | 2.08 (1.24-3.49) | 0.006 | |
| HLA-SE | 0 | 27(39) | 259 (57) | Reference | -- |
| 1 | 31 (45) | 161 (36) | 1.85 (1.06-3.21) | 0.029 | |
| 2 | 11 (16) | 33 (7) | 3.20 (1.45-7.04) | 0.004 | |
| Smoking | Never | 15 (23) | 185 (42) | Reference | -- |
| Ever | 49 (77) | 251 (58) | 2.41 (1.31-4.43) | 0.005 | |
| Smoking | Never | 15 (23) | 185 (42) | Reference | -- |
| Ex-smoker | 28 (44) | 161 (37) | 2.15 (1.12-4.16) | 0.024 | |
| Current smoker | 21 (33) | 90 (21) | 2.88 (1.42-5.85) | 0.003 | |
| HLA-SE positive subgroup | |||||
| Smoking | Never | 10(27) | 77 (45) | Reference | -- |
| Ever | 27 (73) | 95 (55) | 2.19 (1.00-4.80) | 0.051 | |
| Smoking | Never | 10 (27) | 77 (45) | Reference | -- |
| Ex-smoker | 13 (35) | 57 (33) | 1.76 (0.72-4.29) | 0.22 | |
| Current smoker | 14 (38) | 38 (22) | 2.84 (1.15-6.98) | 0.023 | |
| HLA-SE negative subgroup | |||||
| Smoking | Never | 4 (18) | 99 (43) | Reference | -- |
| Ever | 18 (82) | 130 (57) | 3.43 (1.12-10.45) | 0.030 | |
| Smoking | Never | 4 (18) | 99 (43) | Reference | -- |
| Ex-smoker | 11 (50) | 89 (39) | 3.06 (0.94-9.95) | 0.063 | |
| Current smoker | 7 (32) | 41 (18) | 4.23 (1.17-15.22) | 0.027 | |
HLA-SE: shared epitope, ACPA: anti-citrullinated protein antibody, CSA: clinically suspect arthralgia, OR: odds ratio, CI: confidence interval
*
Numbers on smoking in HLA-SE strata do not add up to numbers in the total CSA-group as some patients with data on smoking have missing data on HLA-SE.