Table 2.

Association between hospital and physician volume and complication (n=7,950)

Covariates	Hospital			Surgeon
	Low	Medium	High	Low	Medium	High
	Odds ratio (CI)	Odds ratio (CI)	Odds ratio (CI)	Odds ratio (CI)	Odds ratio (CI)	Odds ratio (CI)
Ethnicity
African American	0.81 (0.69, 0.95)	1.39 (1.13,1.62)	1.15 (0.96,1.33)	1.01 (0.87, 1.14)	1.23 (1.09, 1.46)	0.98 (0.76,1.20)
Hispanic	0.99 (0.86, 1.13)	1.15 (0.92,1.39)	1.12 (0.90,1.34)	1.05 (0.92, 1.18)	1.01 (0.78, 1.24)	1.02 (0.75,1.29)
White (reference)	1.00	1.00	1.00	1.00	1.00	1.00
Age	1.05 (1.03, 1..07)	1.03 (1.01,1.04)	1.03 (1.02,1.05)	1.06 (1.04, 1.06)	1.02 (1.01, 1.04)	1.01 (0.99,1.03)
Income	0.99 (0.99, 0.99)	0.99 (0.99,0.99)	0.99 (0.99,0.99)	0.99 (0.99,0.99)	1.01 (1.0, 1.03)	1.01 (1.00, 1.03)
Married	0.94 (0.84, 1.05)	0.74 (0.66,0.89)	1.04 (0.90,1.18)	0.99 (0.89,1.08)	0.77 (0.62, 0.92)	0.93 (0.78,1.08)
TNM stage
T2b –T2c	1.08 (0.98, 1.17)	1.04 (0.93,1.15)	0.98 (0.87,1.08)	1.12 (1.04, 1.20)	0.87 (0.74, 0.98)	1.06 (0.95,1.18)
≥ T3a	1.29 (1.15, 1.44)	0.81 (0.67,1.09)	0.91 (0.65,1.16)	1.26 (1.12, 1.40)	1.10 (0.76, 1.15)	0.77 (0.52,1.06)
≤ T2a (reference)	1.00	1.00	1.00	1.00	1.00	1.00
Geographic area
Metro	0.76 (0.59, 1.13)	1.04 (0.67,1.54)	1.22 (0.83, 1.61)	0.86 (0.53, 1.21)	0.85 (0.58, 1.28)	1.38 (0.89,1.86)
Urban	1.15 (0.76, 1.49)	1.12 (0.59,1.63)	1.43 (1.03, 1.84)	1.11 (0.86, 1.46)	1.06 (0.68, 1.50)	1.61 (0.89,1.11)
Rural (reference)	1.00	1.00	1.00	1.00	1.00	1.00
Charlson comorbidity
1–2	1.29 (1.15, 1.45)	1.21 (1.03,1.39)	1.24 (1.08,1.39)	1.39 (1.27, 1.51)	1.11 (0.92, 1.30)	1.22 (1.01,1.42)
>3	1.21 (0.95, 1.46)	1.22 (0.93,1.51)	1.26 (1.03,1.49)	1.35 (1.14, 1.55)	0.85 (0.51, 1.22)	1.46 (1.20,1.71)
(reference) 0	1.00	1.00	1.00	1.00	1.00	1.00

CI=confidence interval;