Table 2

Prior appendicectomy or tonsillectomy in people with ulcerative colitis or Crohn's disease: observed (Obs) and expected (Exp) numbers of people with each operation and ratios of observed to expected (O/E), with their 95% confidence intervals (CI)

			Ulcerative colitis				Crohn's disease
Operation	Age in years at operation	Years from operation	Obs	Exp	O/E	95% CI	Obs	Exp	O/E	95% CI
Appendicectomy	<20	<1	1	1.6	0.63	0 to 3.59	14	2.0	7.16	3.90 to 12.05
		1–4	4	7.9	0.51	0.13 to 1.31	12	11.2	1.07	0.55 to 1.87
		≥5	17	36.4	0.47	0.27 to 0.75	28	39.5	0.71	0.47 to 1.03
		All	22	45.6	0.48	0.30 to 0.73	54	53.2	1.02	0.76 to 1.33

	≥20	<1	11	6.2	1.78	0.88 to 3.20	40	5.5	7.31	5.22 to 9.96
		1–4	24	21.6	1.11	0.71 to 1.66	36	17.0	2.12	1.48 to 2.93
		≥5	62	52.5	1.18	0.90 to 1.51	32	33.5	0.95	0.65 to 1.35
		All	97	80.5	1.21	0.98 to 1.47	108	56.2	1.92	1.58 to 2.32

	All ages	All	119	125.9	0.95	0.78 to 1.13	162	107.6	1.51	1.28 to 1.76

Tonsillectomy	<20	<1	2	1.5	1.35	0.13 to 4.96	1	1.9	0.53	0 to 3.01
		1–4	6	6.9	0.87	0.31 to 1.90	17	11.2	1.51	0.88 to 2.43
		≥5	75	84.1	0.89	0.70 to 1.12	120	105.5	1.14	0.94 to 1.36
		All	83	92.9	0.89	0.71 to 1.11	138	119.2	1.16	0.97 to 1.37

	≥20	<1	3	2.9	1.05	0.20 to 3.11	1	2.8	0.36	0 to 2.06
		1–4	10	9.7	1.03	0.49 to 1.90	5	9.1	0.55	0.17 to 1.29
		≥5	19	19.2	0.99	0.59 to 1.54	15	14.7	1.02	0.57 to 1.69
		All	32	31.1	1.03	0.70 to 1.45	21	26.4	0.80	0.49 to 1.22

	All ages	All	115	124.2	0.93	0.76 to 1.11	159	144.9	1.10	0.93 to 1.28