Table 1.
Key model parameters and calibration data.
| Parameter | Prior parameter distribution/calibration range | Source |
|---|---|---|
| Cohort characteristics | ||
| PWID population size* | 9750–17 150 | [30] |
| Proportion of PWID who are female* | 14.7% (95% CI = 13.1–16.4) | TLC-IDU [10] |
| Average duration of injecting drug use (years) | Uniform: 1.75–7.0 | TLC-IDU [10] |
| HIV prevalence among male PWID in 2015* | 9.6% (95% CI = 8.2–11.0) | TLC-IDU [10] |
| HIV prevalence among female PWID in 2015* | 29.1% (95% CI = 19.8–38.4) | TLC-IDU [10] |
| ART coverage among HIV-positive PWID in 2015* | 65.7% (95% CI = 60.3–71.0) | TLC-IDU[10] |
| Proportion of PWID on ART that are virally suppressed | Normal: 34.3% (95% CI = 28.3–40.2) | TLC-IDU [10] |
| HCV antibody prevalence among PWID in 2015* | 10.9% (95% CI = 8.4–13.3) | TLC-IDU [10] |
| Proportion of HCV infections that spontaneously clear among HIV-negatives among HIV-positives | Uniform: 0.22–0.29 | [31] |
| Uniform: 0.115–0.193 | [32] | |
| Efficacy of interventions | ||
| Relative reduction in HCV transmission risk if on OST | Log-normal: 0.50 (95% CI = 0.40–0.63) | [33] |
| Relative reduction in HCV transmission risk if on NSP | Log-normal: 0.44 (95% CI = 24–0.80) | [33] |
| Relative reduction in HIV transmission risk if on OST | Log-normal: 0.46 (95% CI = 0.32–0.67) | [34] |
| Relative reduction in HIV transmission risk if on NSP | Log-normal: 0.42 (95% CI = 0.22–0.81) | [35] |
| HCV disease progression rates | ||
| F0–F1 (per year) | Normal (0.128, 0.0245) | [36] |
| F1–F2 (per year) | Normal (0.059, 0.012) | [36] |
| F2–F3 (per year) | Normal (0.078, 0.0112) | [36] |
| F3–F4 (per year) | Normal (0.116, 0.0232) | [36] |
| Relative increase in HCV disease progression from F0 to F4 if HIV infected | ||
| Without ART | Log-normal: 2.489 (95% CI = 1.811–3.420) | [37] |
| With ART | Log-normal: 1.723 (95% CI = 1.059–2.804) | [37] |
| Annual probability of HCV progression from F4 to decompensated cirrhosis | Beta (14.6168, 360.1732) | [38] |
| Annual probability of HCV progression from F4 to hepatocellular carcinoma | Beta (1.9326, 136.1732) | [38] |
| Annual probability of HCV progression from decompensated cirrhosis to hepatocellular carcinoma | Beta (1.9326, 136.1732) | [38] |
| Annual probability of mortality from decompensated cirrhosis | Beta (147.03, 983.97) | [38] |
| Factor increase in mortality rate from decompensated cirrhosis if HIV co-infected | Log-normal: 2.26% (95% CI = 1.51–3.38) | [39,40] |
| Annual probability of mortality from hepatocellular carcinoma | Beta (117.1033, 155.23) | [38] |
| Relative risk of progression from F4 to decompensated cirrhosis following SVR | Log-normal: 0.07% (95% CI = 0.03–0.2) | [41] |
| Relative risk of progression from F4 to hepatocellular carcinoma following SVR | Log-normal: 0.23% (95% CI = 0.16–0.35) | [42] |
| Disability weights | ||
| HIV disease states | ||
| Acute infection | Equal to ART value | No GBD estimate so assumed equal to ART |
| Chronic infection | Equal to ART value | No GBD estimate so assumed equal to ART |
| HIV: symptomatic, pre-AIDS | Uniform (0.184, 0.377) | [43] |
| AIDs: not on ART | Uniform (0.406, 0.743) | [43] |
| HIV/AIDs: receiving ART | Uniform (0.052, 0.111) | [43] |
| HCV disease states | ||
| METAVIR FO | Not sampled | |
| METAVIR F1-F3 | [67] Assumed linear disability increase from F0 to F4 | |
| METAVIR F4 | Uniform (0.078, 0.159) | [67] No GBD estimate so used value for moderate abdominopelvic problem |
| Decompensated cirrhosis | Uniform (0.123, 0.250) | [67] Decompensated Cirrhosis of the liver |
| Hepatocellular carcinoma | Uniform (0·307, 0·600) | [67] Cancer: metastatic |
| HIV/HCV co-infection | Not sampled | Disability weights were compounded multiplicatively |
| HCV disease state costs ($ | ||
| METAVIR FO | 38 | [44] Sensitivity analysis |
| METAVIR F1–F3 | 76 | [44] Sensitivity analysis |
| METAVIR F4 | 89 | [44] Sensitivity analysis |
| Decompensated cirrhosis | 994 | [44] Sensitivity analysis |
| Hepatocellular carcinoma | 1827 | [44] Sensitivity analysis |
AIDS = acquired immune deficiency syndrome; ART = antiretroviral therapy; GBD = Global Burden of Disease; HCV = hepatitis C virus; HIV = human immunodeficiency virus; KAIS = Kenya AIDS Indicator Survey; NSP = needle and syringe exchange programme; OST = opioid substitution therapy; PWID = people who inject drugs; SVR = sustained virologic response; TLC-IDU = test and linkage to care for injecting drug users.
*
Calibration data.