Table 3.

c statistics for Models 1 to 5, and change between models

Low-value procedure	Model 1 c	Model 2 (hospital) c ∆M1 (95% CI)	Model 3 (LHD) c ∆M1 (95% CI)	Model 4 (SLA) c ∆M1 (95% CI)	Model 5 (all 3 levels)
					c	∆M2	∆M3	∆M4
Sentinel lymph node biopsy for early melanoma	0.69	0.83	0.76	0.77	0.86	0.03	0.10	0.09
		0.14 (0.11–0.17)	0.07 (0.05–0.10)	0.08 (0.07–0.10)		(0.03–0.04)	(0.08–0.12)	(0.07–0.11)
Carotid endarterectomy in asymptomatic high risk patients	0.66	0.76	0.73	0.73	0.78	0.02	0.05	0.05
		0.10 (0.07–0.12)	0.07 (0.05–0.09)	0.07 (0.05–0.08)		(0.01 to 0.02)	(0.03–0.06)	(0.03–0.06)
EVAR in asymptomatic high risk patients	0.61	0.66	0.66	0.68	0.69	0.03	0.03	0.01
		0.06 (0.03–0.09)	0.05 (0.02–0.08)	0.08 (0.07–0.10)		(0.02 to 0.04)	(0.02 to 0.04)	(− 0.02 to 0.03)
Knee arthroscopy for osteoarthritis	0.75	0.83	0.78	0.78	0.83	0.00	0.06	0.05
		0.08 (0.07–0.08)	0.03 (0.02–0.03)	0.03 (0.03–0.03)		(0.00–0.01)	(0.05–0.06)	(0.05–0.05)
ERCP without cholangitis or obstruction	0.72	0.77	0.75	0.75	0.78	0.01	0.03	0.03
		0.05 (0.03–0.06)	0.02 (0.01–0.03)	0.021 (0.02–0.03)		(−0.01 to 0.01)	(0.02–0.04)	(0.02–0.05)
Abdominal hysterectomy	0.63	0.71	0.67	0.69	0.72	0.00	0.04	0.02
		0.09 (0.08–0.09)	0.04 (0.04–0.05)	0.06 (0.06–0.07)		(0.00–0.00)	(0.04–0.05)	(0.02–0.03)
Spinal fusion for low back pain	0.74	0.81	0.81	0.85	0.88	0.07	0.07	0.03
		0.07 (0.05–0.09)	0.06 (0.04–0.08)	0.10 (0.08–0.12)		(0.05–0.08)	(0.05–0.09)	(0.02–0.05)
Colonoscopy for constipation in people < 50 years	0.64	0.76	0.69	0.71	0.78	0.01	0.09	0.06
		0.13 (0.12–0.14)	0.05 (0.04–0.06)	0.07 (0.06–0.08)		(0.01–0.01)	(0.08–0.10)	(0.06–0.07)
Endoscopy for dyspepsia in people < 55	0.62	0.78	0.68	0.73	0.79	0.01	0.10	0.06
		0.16 (0.15–0.17)	0.06 (0.06–0.07)	0.10 (0.10–0.11)		(0.00–0.01)	(0.10–0.11)	(0.06–0.07)

For details of the models, see Table 2. ERCP endoscopic retrograde cholangiopancreatography, EVAR endovascular repair of abdominal aortic aneurysm