Table 1.
Summary of main baseline model parameters with associated uncertainty ranges. Rates are per year.
| Parameter | Baseline value or fitted range when stated [Uncertainty Distribution/Range] |
Source |
|---|---|---|
| Demographic Parameters | ||
| Average population growth rate per year | Pre-2000: Fitted 2.76% [2.53–2.99%] | Pakistan Economic Survey14; United Nations Department of Economic and Social Affairs, Population Division15 |
| Interim 2000–2015: Fitted 1.92% [1.54–2.31%] Post-2015: [Uniform 1.35–2.08%] | ||
| Proportion of Young Adults who initiate injecting drug use | Fitted values: Male: 0.032 [0.026–0.039], Female: 0.009 [0.0004–0.017] |
Calibrated to fit proportion of adults that are PWID (people aged 15 to 64; Male: 0.7%, Female: 0.01%)17 |
| Average mortality rate in each age group | Based on a life expectancy at birth of 66 years in 2015, and adjusted in model calibration to give proportion in each age group in 2015 (Young: 44%, Young Adult: 19%, Adult: 37%)15 | |
| Young Young Adult Adult |
1/56 | |
| 1/41 | ||
| Fitted values: Male: 0.023 [0.020–0.026] Female: 0.020 [0.017–0.024] | ||
| Additional drug-related mortality rate | 0.028 [Lognormal 0.017–0.039] | Based on estimates of drug-related mortality across Asia10 |
| Transmission Parameters | ||
| HCV transmission rate per susceptible in each age group |
β1 = 0.059 [0.052–0.066] β2 = 0.053 [0.023–0.085] β3 = 0.12 [0.10–0.14] |
Fit to chronic prevalence in each age category from 2007–2008 Pakistan national survey7 on viral hepatitis (Young: 1.5%, Young Adult: 3.2%, Adult: 6.9%) |
| Additional HCV transmission rate for injecting drug use | 0.61 [0.51–0.74] | Fit to chronic prevalence in PWID16 in 2012: 62.2% [55.5–68.8%] |
| Proportion of infections that spontaneously clear | 0.26 [Uniform 0.22–0.29] | Systematic review of spontaneous HCV clearance12 |
| Treatment Parameters | ||
| Treatment rate per capita before 2018 | Calibrated to historical treatment rates† | Pakistan Health Research Council (unpublished data) |
| Average duration on treatment | 24-weeks prior to 2016. Shortened to 12 weeks for pre-cirrhotic patients and 24 weeks for post-cirrhotic patients from 2016 onwards | World Health Organization HCV Treatment Guidelines13 |
| SVR rate with IFN and RBV treatment | 0.61 [Uniform 0.50–0.73] | Studies on SVR rates for conventional HCV treatment in Pakistan18 |
| SVR rate with new DAA treatments | 0.9 [Uniform 0.80–0.95] | World Health Organization HCV Treatment Guidelines13; Review of DAAs in Pakistan19 |
†
Total estimated historical HCV treatments prior to 2018, assuming a public/private sector split of 40%/60% (Supplementary Table S3). 2005–2010: 57,500; 2011: 137,970; 2012: 129,398; 2013: 137,910; 2014: 115,920; 2015–2017: 152,710 treatments. DAAs available from 2016 onwards.
‡
Abbreviations. DAA: direct-acting antiviral; HCV: hepatitis C virus; IFN: interferon; PWID: people who inject drugs; RBV: ribavirin; SVR: sustained virologic response.