Table 3. Crude and adjusted odds ratios for perforated appendicitis, by surgeon acute appendicitis case volume.

Variables	Crude odds ratio		Adjusted odds ratio
	95% CI	P value	95% CI	P value
Surgeon acute appendicitis case volume
≤65	1.00		1.00
66∼120	0.95 (0.90–0.99)	0.031	0.92 (0.87–0.96)	<0.001
121∼190	0.91 (0.86–0.95)	<0.001	0.86 (0.82–0.91)	<0.001
≥191	0.70 (0.66–0.73)	<0.001	0.66 (0.62–0.70)	<0.001
Surgeon characteristics
Practice location
Urban	1.19 (1.14–1.24)	<0.001	1.09 (1.03–1.14)	<0.001
Rural	1.00		1.00
Hospital teaching status
Yes	1.62 (1.52–1.73)	<0.001	1.61 (1.49–1.73)	<0.001
No	1.00		1.00
Patient characteristics
Patient age (years)
≤19	1.00		1.00
20∼39	0.64 (0.61–0.67)	<0.001	0.65 (0.62–0.68)	<0.001
40∼59	1.20 (1.14–1.27)	<0.001	1.18 (1.12–1.24)	<0.001
≥60	2.44 (2.31–2.59)	<0.001	2.19 (2.06–2.33)	<0.001
Patient gender
Male	1.28 (1.23–1.32)	<0.001	1.33 (1.28–1.38)	<0.001
Female	1.00		1.00
Charlson Comorbidity Index score
0	1.00		1.00
1	2.36 (2.21–2.53)	<0.001	1.54 (1.43–1.66)	<0.001
2	3.17 (2.71–3.72)	<0.001	1.81 (1.53–2.13)	<0.001
3 or more	3.42 (2.95–3.95)	<0.001	2.01 (1.73–2.35)	<0.001
Hospital appendicitis case volume	1.00 (1.00–1.00)	<0.001	1.00 (1.00–1.00)	<0.001