Background: Repeat HIV testing during pregnancy/breastfeeding can help detect new maternal HIV infections and prevent mother-to-child HIV transmission (MTCT). Many African countries have introduced repeat testing approaches; however, economic analysis and public health impact of approaches have not been conducted.
Methods: We constructed a Markov decision-analytic cohort model for MTCT to assess the cost-effectiveness of repeat testing in Kenya and South Africa. Model parameters incorporate maternal HIV infection status and stage of seroconversion, pregnancy/postpartum status, maternal antiretroviral therapy, infant antiretrovirals, and viral suppression. We estimated the potential impact of varying the timepoint and frequency of repeat maternal testing on infant HIV infections averted under various testing scenarios:
1) late gestation/delivery,
2) 6 weeks postpartum,
3) 6 months postpartum, and
4) late gestation/delivery plus 6 weeks postpartum.
Repeat testing was cost-effective if the incremental cost-effectiveness ratio (ICER) was < 3 times the threshold national per capita gross domestic product (US$1500 in Kenya and US$5500 in South Africa).
Results: Assuming a population of 1,600,000 for each country, the number of infant infections averted during pregnancy and through 12 months postpartum attributed to repeat maternal testing ranged from 2,296-6,289 in Kenya and 2,960-42,454 in South Africa (Tables) under scenarios 3 and 4, respectively. The ICER for repeat maternal HIV testing ranged in Kenya from $440 (scenario 1) to $3,113 (scenario 3) and in South Africa from $461 (scenario 1) to $3,285 (scenario 3) per infant infection averted. Compared to the base case model, repeat testing at 2 time points (scenario 4) averts the largest proportion of MTCT (21% reduction in Kenya vs. 34% in South Africa). Using a single repeat testing strategy, repeat testing during late gestation/delivery resulted in the largest reduction in MTCT (16% in Kenya vs. 30% in South Africa).
Conclusions: In our model, all repeat maternal testing scenarios were cost-effective and averted infant infections in Kenya and South Africa, but repeat testing in late pregnancy/delivery or at 6 weeks postpartum resulted in substantially larger reductions in MTCT than at 6 months after delivery. These findings have important implications for designing repeat testing approaches as a strategy to prevent MTCT and improve maternal health.

Testing strategy (a)Incremental costs (b)Infant infections averted (b)ICER (b)Percent of maximum potential benefit achieved (c)
Strategy 116,650,53137,85244030.5
Strategy 212,650,57311,9731,0579.7
Strategy 39,216,2962,9603,1132.4
Strategy 423,033,30142,45454334.3
Cost effectiveness analysis results. a) Strategy 1= testing at first antenatal care (ANC) visit and in late gestation or delivery; strategy 2= testing at first ANC, 6 week maternal child health (MCH) visit; strategy 3= testing at first ANC, and 6 month MCH visit; strategy 4=testing at first ANC, late gestation or delivery, and 6 week MCH visit. b) ICER= incremental cost effectiveness ratio, in 2017 US$ per infant infection averted; base case assumes testing at first ANC only. c) The percent of maximum potential benefit achieved is the number of infant infections that could be averted by the testing strategy divided by the total number of infants expected to be infected under the base case scenario (testing at first ANC alone) in a population restricted to women eligible for HIV testing under model assumptions.
[Table 1: Cost-effectiveness of repeat maternal HIV testing under model scenarios, South Africa]

Table 2:Cost-effectiveness of repeat maternal HIV testing under model scenarios, Kenya
[Table 2:Cost-effectiveness of repeat maternal HIV testing under model scenarios, Kenya]