Cost-effectiveness of emergency department opt-out testing for HIV in England: a modelling study

Background: In England, up to 5% of people living with HIV remained undiagnosed and the proportion of late diagnoses remains high, but opt-out testing can help to identify people living with undiagnosed HIV who may not access testing in other settings. We aimed to evaluate the cost-effectiveness of the first phase of NHS-funded opt-out testing for HIV in emergency departments which scaled up from 2022.<br/><br/>Methods: We adapted a previously-developed deterministic model of HIV diagnosis, progression, and transmission to simulate the impact of the first 33 months of the opt-out testing intervention in improving HIV diagnosis, incorporating programme data on CD4 count at diagnosis. We conducted a bottom-up costing of the intervention in two sites, from a National Health Service perspective, and gathered costs of HIV care from literature. In the base case we assumed 93% of new diagnoses would not have been diagnosed elsewhere during the programme as these individuals had never previously been tested for HIV. Cost-effectiveness is presented as incremental costs per quality-adjusted life year (QALY) gained over 20 years compared to the £25,000-£35,000/QALY threshold; we explored scenario analysis to address the limitations of the model assumptions.<br/><br/>Results: The average cost per HIV test was £6.31 (US$7.91). Under base case assumptions, emergency department opt-out testing is projected to avert 187 HIV-related deaths and 28 secondary infections over 20 years, costing £18,630 (£17,413-£23,119) (US$23,343) per QALY gained. This result is robust (below £35,000/QALY) to different assumptions about HIV-related quality of life and HIV care costs, HIV-related mortality, and the rate of diagnosis outside of the programme. Under a lower test yield scenario of 0.2 new diagnoses per thousand tests (compared to 0.29 in the base case), the intervention remains cost-effective at £25,000/QALY. <br/><br/>Interpretation: Opt-out testing for HIV in England was cost-effective due to averted HIV-related morbidity and mortality resulting from improving diagnosis and linkage to care of people who would otherwise not be tested, many of whom had already reached an advanced stage of HIV progression. This provides evidence to support the continuation of the opt-out testing programme as part of the HIV action plan. <br/>