Table 1. Assumptions, data sources, uncertainty estimates, impacts on outcomes, and sensitivity analyses.

Base Case Assumption	Rationale	Main Data Source	Impact SA
Price and economic parameters
Published ex-factory prices were used.	Pharmacy retail prices contain taxes and elements of distribution remuneration, which would limit comparability.	PPI service	Impact: underestimates total expenditure. SA: not applicable.
Purchasers in all countries received a 23% price reduction, except for countries with a negotiated tiered price.	Levels of rebate/discounts were mostly confidential; we applied the disclosed rebate obtained by the US Centers for Medicare & Medicaid Services (i.e., 23%).	[17]	Impact: underestimates total expenditure because not all countries would receive such large discounts. SA: tested 50% rebate according to Pollack [42] and 0% rebate (S2 Text).
Average or median wages were used as an indicator of income among the population with HCV infection.	People with HCV infection were assumed to have the same income as the general population. This is a conservative assumption because intravenous drug users are most at risk of HCV infection and typically have low incomes, low employment, and low education levels [36,37].	[43,44]	Impact: likely underestimates out-of-pocket expenditure. SA: assumed HCV population had minimum wage based on Country Reports on Human Rights Practices for 2014 [45], for comparability with previous studies [38–40] (S2 Text).
Patients were assumed to pay 100% of the cost of treatment in the affordability analysis.	Coverage of HCV medicines and level of co-payment vary by country.	[17–19]	Impact: applicable for individuals without adequate insurance coverage or whose coverage does not include HCV medicines. The financial impact of HCV treatment on these individuals is underestimated because ex-factory prices (not retail prices) were used. SA: not applicable.
Demographic, epidemiological, and treatment parameters
All patients received 12-wk treatment.	12-wk treatment is recommended for all HCV genotypes, except for genotype 3 (24-wk treatment recommended). Most patients have non–genotype 3 HCV.	[33]	Impact: underestimates cost of 24 wk of treatment. SA: assumed patients with genotype 3 HCV received 24-wk treatment (S3 Text).
Treatment price did not include ribavirin or other supplementary therapies.	Supplementary therapies are dependent on patient characteristics, and global data on these characteristics were largely unavailable.	[33]	Impact: underestimates the overall cost of HCV treatment. SA: not applicable.
Point estimates for prevalence of viraemic HCV were used.	Prevalence estimates based on anti-HCV antibodies overestimate the demand for treatment because ~25% of persons who acquire HCV clear the infection spontaneously.	[1,31,32]	Impact: may overestimate treated population. SA: ranges of estimates of viraemic populations are presented.

SA, sensitivity analysis.