Risk of having a positive or negative stool test for enteric bacteria following a diagnosis of Crohn's disease or ulcerative colitis, Denmark, 1992–2008
| Positive test | Negative test | |||||
| Salmonella | Campylobacter | |||||
| Cases, n | IRR (95% CI) | Cases, n | IRR (95% CI) | Cases, n | IRR (95% CI) | |
| Background population* | 68 784 | 1 (reference) | 46 947 | 1 (reference) | 120 541 | 1 (reference) |
| Patients with Crohn's disease: time since diagnosis | ||||||
| <1 year | 71 | 11.5 (8.5 to 15.5) | 55 | 10.4 (8.0 to 13.5) | 317 | 28.4 (25.3 to 31.5) |
| 1–10 years | 118 | 2.7 (2.1 to 3.5) | 83 | 2.3 (1.9 to 2.9) | 241 | 3.2 (2.8 to 3.6) |
| >10 years | 71 | 1.9 (1.4 to 2.6) | 69 | 2.5 (1.9 to 3.1) | 34 | 3.1 (2.2 to 4.3) |
| Overall | 260 | 3.0 (2.6 to 3.4) | 207 | 3.0 (2.6 to 3.4) | 592 | 6.4 (6.1 to 6.7) |
| Patients with ulcerative colitis: time since diagnosis | ||||||
| <1 year | 222 | 14.9 (12.5 to 17.6) | 149 | 12.8 (10.9 to 15.1) | 924 | 34.0 (31.9 to 36.3) |
| 1–10 years | 278 | 2.9 (2.4 to 3.3) | 182 | 2.5 (2.2 to 2.9) | 536 | 3.4 (3.1 to 3.7) |
| >10 years | 153 | 2.0 (1.7 to 2.5) | 126 | 2.7 (2.3 to 3.3) | 88 | 4.6 (3.8 to 5.7) |
| Overall | 653 | 3.6 (3.3 to 3.9) | 457 | 3.5 (3.2 to 3.9) | 1548 | 8.2 (8.0 to 8.5) |
↵* The background population consists of the Danish population without a record of Crohn's disease or ulcerative colitis recorded in the Danish National Patient Register between 1977 and 2008.
IRR, incidence rate ratio.