Mathematical modeling to assess health and economic impact of cardiovascular interventions and implementation strategies among people living with HIV: SAIA HTN.

backgroundFew economic evaluations distinguish between the cost and impact of evidence-based interventions and the strategies used to improve their implementation. This distinction is essential for understanding whether a strategy is cost-effective, why it works, and the resources required to replicate its success. The Systems Analysis and Improvement Approach Hypertension (SAIA-HTN) trial evaluated an implementation strategy ("SAIA") designed to improve hypertension care among people living with HIV (PLHIV) in Mozambique. We developed a mathematical model to estimate the cost-effectiveness of both the evidence-based intervention (including hypertension screening, pharmacological treatment and follow up, and lifestyle modifications such as diet and exercise) and the SAIA implementation strategy.

methodsWe constructed a decision-analytic, state-transition model that simulated cardiovascular risk, outcomes, and associated costs for PLHIV receiving hypertension care in Mozambique using a health systems perspective. Model inputs came from published epidemiological studies and primary data from the SAIA-HTN trial on intervention and implementation strategy effectiveness and costs. We estimated the incremental cost-effectiveness (willingness to pay $647/DALY averted, GDP per capita in Mozambique) of rolling out both components, compared to a "status quo" scenario where screening and treatment of hypertension remained at their current (very low) levels. Costs were reported in 2023 US dollars, and costs and outcomes were discounted at 3% over a ten-year time horizon.

resultsScaling up screening and pharmacological treatment of hypertension in Mozambique would have an incremental cost-effectiveness ratio (ICER) of around $212 per disability-adjusted life year (DALY) averted and cost an additional $4.61 per person per year. Incremental to the intervention, the SAIA implementation strategy would have an ICER of $44 per DALY averted and cost an additional $0.79 per person per year. The average reduction in ten-year cardiovascular risk would be 29.3% for the intervention and 40.3% if the SAIA implementation strategy were co-introduced.

conclusionsOur model is a tool for implementation scientists, policymakers, and researchers aiming to assess cardiovascular interventions and associated implementation strategies among PLHIV. Its application to SAIA-HTN suggests that this is a cost-effective strategy for improving hypertension care, but only in the presence of adequate blood pressure equipment, training, and medications. Our study shows how implementation strategies require a minimum threshold of health system readiness to generate meaningful health impact.

trial registrationClinicalTrials.gov (NCT04088656).