Table 1. Model Parameters.
| Description | Estimate or Range* | Reference | |
| Test rate | 10–20% | Macha, Zambia | |
| Rate of being tested in the acute stage of HIV | 50% of the test rate | Assumption** | |
| Rate of being tested in the chronic stage of HIV | test rate | Macha, Zambia | |
| Rate of being tested in the AIDS stage | test rate +10% | Macha, Zambia | |
| Disease stages duration | [10], [11], [12], [13] | ||
| Acute stage | 10–16 weeks | ||
| Chronic stage | 8.31–8.43 years | ||
| AIDS stage | 6–12 months | ||
| Final AIDS stage | 7–13 months | ||
| Proportion of people in sexual risk groups | Model Calibration | ||
| Highest *** | 1.0%–2.9% | ||
| 2nd *** | 15.1%–24.0% | ||
| 3rd | 10% | ||
| Lowest | 63.1%–73.9% | ||
| Number of partners per year in each sexual risk group | Model Calibration | ||
| Highest *** | 7–31 | ||
| 2nd *** | 1.5–2.6 | ||
| 3rd | 0.1 | ||
| Lowest | 0.03 | ||
| Mortality rates per year | [39] | ||
| Population | 0.02 | ||
| Chronic HIV stage | 0.098 | ||
| AIDS stage | 0.63 | ||
| On treatment during chronic stage, first 3 months | 0.05–0.098 | ||
| On treatment during chronic stage, second 3 months | 0.03–0.06 | ||
| On treatment during chronic stage, 6+ month | 0.02–0.05 | ||
| On treatment during AIDS stage, first 3 months | 0.1–0.3 | ||
| On treatment during AIDS stage, second 3 months | 0.05–0.12 | ||
| On treatment during AIDS stage, 6+ month | 0.03–0.06 | ||
| Linkage to care from test to treat | 70% | Macha, Zambia | |
| Proportion of people on PrEP | |||
| Non-prioritized PrEP | 40–60%† | Assumption | |
| Prioritized PrEP (approximately half of highest two sexual risk groups) | 5–15%‡ | Assumption | |
| Effectiveness of PrEP | [2], [3], [4] | ||
| Moderate Adherence | 20–60% | ||
| High Adherence | 50–90% | ||
| Reduction in transmissibility of those patients on treatment | 90–100% | [25], [26], [27] | |
| Rate of resistance among those infected despite use of PrEP | 10%, 50%, 100% | Assumption | |
| Rate of discontinuation of PrEP (not due to resistance) | 4–5% | [40] | |
| Number of HIV tests per year on PrEP | 1–4 | Assumption | |
| Number of HIV clinic visits in first year | 8 | Macha, Zambia | |
| Number of yearly HIV clinic visits after first year | 4 | Macha, Zambia | |
| Costs | |||
| Cost of PrEP per year (TDF/FTC) (§) | $126 ($137.12) | [28], [29] | |
| Cost of testing negative for HIV per test (§) | $1 ($3.78) | Macha, Zambia, [28] | |
| Cost of testing positive for HIV per test (§) | $3.84 ($9.4) | Macha, Zambia, [28] | |
| Cost of an inpatient day in the hospital | $10.27 | [28] | |
| Cost of an outpatient visit in the hospital | $2.78 | [28] | |
| Cost of treatment per year (TDF/FTC+EFV) (§) | $194 ($243) | [29] | |
| Cost of a CD4 Count test (§) | $31–$39($34–$42) | Macha, Zambia, [28] | |
| Cost discounting rate per year | 3% | ||
| Exchange rate, Zambian Kwacha to USD over year 2011 | 3845∶1 | ||
*
All ranges are uniformly distributed, except where indicated.
**
Due to window phase of antibody-based test.
***
Not uniformly distributed, see figure S2.
†
Not uniformly distributed, median 43% over 10 years;
‡
Not uniformly distributed, median 12% over 10 years;
§
Comprehensive costs, including costs of outpatient visits, additional laboratory tests, laboratory personnel.