Variable categories, description, expected effect on costs and justification
| Variable category | Variable name | Description | Expected effect on costs | Justification | Source |
| Dependent variable | Average costs per HIVST kit distributed including central costs | Unit costs per HIVST kit distributed including in-country central costs and start-up costs in 2019 US$ | NA | NA | 12 |
| Quantities | Scale | Number of HIVST kit distributed by site during the observation period | ± | (Dis)Economies of scale | PSI |
| Site organisational characteristics | HIVST distributors | Number of full time equivalent HIVST distributor in each site | ± | Increase your coverage and # of HIVST kits distributed (so lower average costs per kit distributed), but also increase personnel costs | PSI |
| Campaign style | Variable coded 1 if the same distributors travel from sites to sites (campaign style distribution) or 0 if they live within the community | + | In some countries, HIVST kits distribution was more conservative and restricted by campaign duration in each site, so this approach could drive costs higher due to lower volumes of kits distributed and travel costs | PSI | |
| Efficiency | Number of HIVST kits distributed per agent per month | – | The higher the number of HIVST kits distributed per agent, the more efficient they are and the lower is the cost per kit distributed | PSI | |
| Characteristics of population targeted | % HIVST kits distributed to men | Number of kits distributed to men – also measure if programme is targeting well (proxy for quality) | + | Men might be harder to reach and to convince to take a kit, might lead to higher costs of provision | PSI |
| % never tested for HIV | % of people who never tested for HIV | – | Higher knowledge of HIV status might lead to lower demand for testing, including HIVST, leading to increased average cost per kit distributed | STAR household surveys | |
| Environmental characteristics | Distance | Distance from central warehouse to site in kilometres | + | Longer distance from the PSI headquarters and warehouse might lead to high costs of service provision | PSI, Google Maps |
| Catchment population | Size of the catchment population of the site regardless of eligibility | – | Number of potential HIVST recipients affect levels of distribution potentially leading to economies of scale | PSI, Ministry of Health | |
| Positivity at health facility | Annual new HIV positive identified over total tested at nearby health facility (positivity rate) | + | If the health facilities experience high positivity rates, the demand for HIVST might be lower leading to increased average costs (higher costs to reach the last % of target population) | PSI, Ministry of Health | |
| HTS average cost at health facility | Average cost per person tested with HTS at the nearest health facility | + | Although not a determinant, a significant correlation might suggest the effect of other unobserved environmental characteristics on costs | 12 24 | |
| Input price level | Price level | Per capita Growth Domestic Product in 2019 US$ | + | Proxy for input price level variation across countries | 52 |
HTS, HIV testing services; PSI, Population Services International; STAR, Self-Testing AfRica.