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.