Standardised incidence ratios and 95% CI of Crohn’s disease among 709 353 patients undergoing appendectomy in Swedish (1964 to 2004) and Danish (1977 to 2004) hospitals stratified by cause of appendectomy
| Cause of appendectomy | Person-years | Obs | Exp | SIR (95% CI) | *p Value |
|---|---|---|---|---|---|
| Exp, Expected number of patients with Crohn’s disease; Obs, observed number of patients with Crohn’s disease; SIR, standardised incidence ratio. | |||||
| *Test of homogeneity. P value < 0.001 whether using a three-way (appendicitis, mesenteric lymphadenitis, other disease) or a six-way (appendicitis with perforation, appendicitis without perforation, mesenteric lymphadenitis, appendiceal disease except appendicitis, non-specific abdominal pain, other and unspecified disease) categorisation of the cause of appendectomy. | |||||
| Appendicitis | 7 188 320 | 924 | 707.6 | 1.31 (1.22 to 1.39) | <0.001 |
| With perforation | 1 234 469 | 216 | 114.2 | 1.89 (1.66 to 2.16) | |
| Without perforation | 5 953 851 | 708 | 593.5 | 1.19 (1.11 to 1.28) | |
| Mesenteric lymphadenitis | 645 698 | 111 | 68.0 | 1.63 (1.36 to 1.97) | |
| Other disease (non-inflamed appendix) | 3 244 837 | 620 | 314.1 | 1.97 (1.82 to 2.14) | |
| Appendiceal disease except appendicitis | 43 437 | 8 | 4.2 | 1.92 (0.96 to 3.83) | |
| Non-specific abdominal pain | 654 377 | 138 | 69.6 | 1.98 (1.68 to 2.34) | |
| Other and unspecified disease | 2 547 023 | 474 | 240.4 | 1.97 (1.80 to 2.16) | |