Table 3.

Sensitivity analysis results shown as mean cost per QALY gained (95% confidence interval) for surgery relative to non-operative care by disease group as analytic assumptions are varied.

Analytic Assumptions	Mean Cost per QALY Gained (95%CI)
	Spinal Stenosis	Degenerative Spondylolisthesis	Intervertebral Disc Herniation
Primary analysis*	$59,400 ($37,059, $125,162)	$64,300 ($32,864, $83,117)	$20,600 ($4,539, $33,088)
Observational Cohort	$48,300 ($12,011, $110,277)	$88,000 ($33,577, $151,986)	$28,200 ($5,283, $54,337)
Randomized Cohort	$124,700 ($35,592, $459,143)	$51,600 ($18,885, $79,327)	$17,700 (save, $33,331)
Direct Medical Costs**	$52,100 ($29,504, $84,516)	$73,200 ($48,906, $87,650)	$26,500 ($16,784, $33,574)
Direct Medical & Worker Productivity Costs	$53,900 ($31,362, $91,012)	$72,200 ($48,124, $88,020)	$26,800 ($14,110, $33,863)
Higher Surgery Payment Amount	$102,400 ($63,558, $180,753)	$122,500 ($78,827, $148,691)	$43,800 ($22,291, $57,563)
With Mortality Adjustment	$63,600 ($32,443, $115,557)	$61,400 ($33,199, $82,307)	$20,700 ($4,571, $33,037)
Initial Surgery Occurred within 2 Years	$52,300 ($28,977, $96,795)	$55,100 ($29,220, $71,046)	$18,500 ($3,457, $29,514)
QALY Estimation with SF-6D	$66,700 ($38,138, $122,820)	$79,300 ($43,314, $109,123)	$28,000 ($5,836, $46,913)

^*Combined randomized and observational cohorts, all costs, Medicare surgery costs, no mortality adjustment, and EuroQol EQ-5D scores used to estimated QALYs.

^**Consistent with reference-case analysis recommended by Panel on Cost-effectiveness in Health and Medicine.