Main technical assumptions for the cost-effectiveness simulation model
| Parameters | Value | (min–max) | Distribution | Sources |
| Healthcare | ||||
| Mother-to-child transmission rate at 6 weeks | 7.7% | Point estimate | PNLSH* | |
| HIV-exposed infant receiving PCR test at 6 weeks | 64.4% | (47.5–81.2) | Random point estimate | 26 |
| Mothers' arrival time at the health centre | 9:00 hours | (7:00–16:30 hours) | Beta PERT | Field survey (online supplemental appendix 3) |
| Waiting time before being seen in consultation (min) | 133.8 | SD: 66.7 | Normal with truncation of negative values | Literature review (online supplemental appendix 4) |
| Time required to perform a PCR test at the central laboratory (min) | 105 | (90 –120) | Random point estimate | Field observations with GeneXpert |
| Work departure time of healthcare workers in postnatal services | 16:30 | Point estimate | Field observations | |
| Mothers able to wait until healthcare workers leave | 40.2% | (10.6–69.9) | Point estimate | Field survey (online supplemental appendix 5) |
| Maximum duration mothers can wait in the health centre (min) | 160 | (3 –570) | Beta PERT | Field survey (online supplemental appendix 5) |
| No of days needed to return for the test results if not collected the same day (median) | 21 | (0–365) | Cumulative gamma | Literature review (online supplemental appendix 6) |
| Median number of days for collection-to-results turnaround times (baseline scenario) | 35 | (0–365) | Cumulative gamma | Literature review (online supplemental appendix 7) |
| ART initiation acceptance rates | 92.3% | Point estimate | 4 | |
| Average age at ART initiation among children after 1 year | 4.7 | (1.0–21.7) | Exponential | IeDEA data (online supplemental appendix 8) |
| UAV | ||||
| UAV price | US$11 562 | Point estimate | DeltaQuad | |
| Operational horizontal speed (km/hour) | 65 | Point estimate | DeltaQuad | |
| Operational vertical speed (km/hour) | 4.32 | Point estimate | DeltaQuad | |
| Flight altitude required (metres) | 80 | Point estimate | Field observations | |
| Autonomy (min) | 110 | Point estimate | DeltaQuad | |
| Maximal flight distance (km) | 100 | Point estimate | DeltaQuad | |
| Preparation times, for example, UAV deployment (min) | 4 | Point estimate | DeltaQuad and Field observations | |
| Weather inoperability | 2.7% | Point estimate | Meteoblue (online supplemental appendix 9) | |
| UAV loss rates (per 100 000 flights) | 2.5 | (0.0–5.0) | Point estimate | Drone Volt, DeltaQuad, assumptions† |
| Motorcycle | ||||
| Motorcycle price | $3238 | Point estimate | CFAO motors Guinea | |
| Lifespan (en km) | 55 000 | (30 000–70 000) | Beta PERT | 14 |
| Breakdown rate (per 10 000 km) | 0.6 | Point estimate | 14 | |
| Minor accident rate (per 100 000 km) | 1.65 | Point estimate | 14 | |
| Major accident rate (per 100 000 km) | 0.43 | Point estimate | 14 | |
| Weather inoperability | 0.2% | Point estimate | Meteoblue (online supplemental appendix 9) |
*Routine data collected in Conakry by the National Programme for HIV and hepatitis (Programme National de Lutte contre Le VIH/Sida et les Hepatites) in 2021 among 881 HIV-exposed children tested at 6 weeks in public health centres (68 positive results).
†We based our assumptions on publicly available data on the Alphabet’s drone service (https://wing.com/) operating on-demand delivery in US, Finland and Australia. To date, 5 crashes have been reported (3 in Australia and 2 in Finland) for a total of 200 000 flights.
ART, antiretroviral therapy; CFAO, Corporation For Africa & Overseas; IeDEA, International epidemiology Databases to Evaluate AIDS; PERT, Program evaluation review technique; UAV, unmanned aerial vehicles.