Incorporating the HIV Infant Tracking System into standard-of-care early infant diagnosis of HIV services in Kenya: a cost-effectiveness analysis of the HITSystem randomised trial

Background: The HITSystem efficacy trial showed significant improvements in early infant diagnosis retention, return and notification of infant test results, and earlier antiretroviral therapy (ART) initiation compared with standard-of-care early infant diagnosis services in Kenya. This study aimed to analyse data from the HITSystem trial to assess the cost-effectiveness of the intervention in Kenya. Methods: In this analysis, we extrapolated results from the HITSystem cluster randomised controlled trial to model early infant diagnosis outcomes and cost-effectiveness if the HITSystem was scaled up nationally in Kenya, compared with standard-of-care outcomes. We used a micro-costing method to collect cost data, which were analysed from a health-system perspective, reflecting the investment required to add HITSystem to existing early infant diagnosis services and infrastructure. The base model used to calculate cost-effectiveness was deterministic and calculated the progression of infants through early infant diagnosis. Differences in progression across study arms were used to establish efficacy outcomes. The number of life-years gained per infant successfully initiating ART were based on the Cost Effectiveness of Preventing AIDS Complications model in east Africa. HITSystem cost data were integrated into the model, and the incremental cost-effectiveness ratio was calculated in terms of cost per life-year gained. Sensitivity analyses were done using the deterministic model with triangular stochastic probability functions for key model parameters added. The number of life-years gained was discounted at 3% and costs were adjusted to 2021 values. Findings: The cost per life-year gained from the HITSystem was US$82·72. Total cost for national HITSystem coverage in Kenya was estimated to be around $2·6 million; covering 82 230 infants exposed to HIV at a cost of $31·38 per infant and a yield of 1133 infants receiving timely ART, which would result in 31 189 life-years gained. With sensitivity analyses, the cost per life-year gained varied from $40·13 to $215·05. 90% of model values across iterations ranged between $55·58 (lower 5% threshold) and $132·38 (upper 95% threshold). Interpretation: The HITSystem would be very cost-effective in Kenya and can optimise the return on the existing investment in the national early infant diagnosis programme. Funding: The US National Institute of Child Health and Human Development.