Table 1.

Model Parameters

Parameter	Base case	Lower	Upper	Probabilistic distribution	Source
General model settings
Patient age (all populations)	40				Assumption
Annual discount rate	3%				Neumann11
Sensitivity analyses, range % +/-	25%				Assumption
Number of probabilistic analysis simulations	5,000				Assumption
Prefunctional decline population assumptions
CAG repeats	40				Advisory board
Total functional capacity (TFC) score	13				Advisory board
Total motor score (TMS)a	2				Advisory board
Symbol digit modalities test (SDMT) scorea	50				Advisory board
Natural history outcomes for SF1 (TFC 13-11)
Total functional capacity (TFC) score baseline	12.2				TRACK-HD16
TFC 12-mo Δ	−0.910	−1.360	−0.620	Normal	TRACK-HD16
TFC 36-mo Δ	−1.989	Correlated		TRACK-HD17
Annual TFC transition probabilityb	0.651	Varies with SLRc		SLR-derivedc
Natural history outcomes for SF2 (TFC 10-7)
Total functional capacity (TFC) score baseline	8.7				TRACK-HD16
TFC 12-mo Δ	−0.440	−0.780	−0.130	Normal	TRACK-HD16
TFC 36-mo Δ	−1.974	Correlated		TRACK-HD17
Annual TFC transition probability	0.669	Varies with SLRc		SLR-derivedc
Health state utilities
Premanifest	0.86	0.84	0.87	Beta	Jiang27
Shoulson and Fahn stage 1 (TFC 11–13)	0.78	0.72	0.85	Beta	Rodríguez-Santana28
Shoulson and Fahn stage 2 (TFC 7–10)	0.66	0.59	0.73	Beta	Rodríguez-Santana28
Shoulson and Fahn stage 3 (TFC 3–6)	0.54	0.48	0.61	Beta	Rodríguez-Santana28
Shoulson and Fahn stage 4–5 (TFC 0–2)	0.22	0.11	0.32	Beta	Rodríguez-Santana28
Direct medical costs
Shoulson and Fahn stage 1 (TFC 13-11)	$13,183	$5,723	$20,644	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 2 (TFC 10-7)	$16,549	$3,786	$29,311	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 3 (TFC 6-3)	$20,189	$5,404	$34,974	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 4 (TFC 2-1)	$48,031	$18,983	$77,080	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 5 (TFC 0)	$25,217	$0	$55,668	Log-normal	Rodríguez-Santana29
Societal costs
Shoulson and Fahn stage 1 (TFC 13-11)	$30,691	$11,333	$50,048	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 2 (TFC 10-7)	$41,676	$15,390	$67,962	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 3 (TFC 6-3)	$110,142	$38,727	$185,849	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 4 (TFC 2-1)	$58,561	$1,724	$115,398	Log-normal	Rodríguez-Santana29
Shoulson and Fahn stage 5 (TFC 0)	$36,409	$1,072	$71,746	Log-normal	Rodríguez-Santana29

^aFor low-education (high school only) population.

^bAlso used for the prefunctional decline (PFD) population once progression commences.

^cSLR = simple linear regression of TRACK-HD baseline, 1-year, and 3-year TFC scores.