Home testing and counselling to reduce HIV incidence in a generalised epidemic setting: a mathematical modelling analysis

Abstract

Background: Home HIV testing and counselling (HTC) achieves high levels of HIV testing and linkage to care. Periodic home HTC, particularly targeted to those with high HIV viral load, might facilitate expansion of antiretroviral therapy (ART) coverage. We used a mathematical model to assess the effect of periodic home HTC programmes on HIV incidence in KwaZulu-Natal, South Africa.

Methods: We developed a dynamic HIV transmission model with parameters, primary cost data, and measures of viral suppression collected from a prospective study of home HTC in KwaZulu-Natal. In our model, we assumed home HTC took place every 5 years with ART initiation for people with CD4 counts of 350 cells per μL or less. For individuals with CD4 counts of more than 350 cells per μL, we compared increasing ART coverage for those with 350-500 cells per μL with initiating treatment for those who have viral loads of more than 10 000 copies per mL.

Findings: Maintaining the presently observed level of 36% viral suppression in HIV-positive people, HIV incidence decreases by 33·8% over 10 years. Home HTC every 5 years with linkage to care with ART initiation at CD4 counts of 350 cells per μL or less reduces HIV incidence by 40·6% over 10 years. Expansion of ART to people with CD4 counts of more than 350 cells per μL who also have a viral load of 10 000 copies per mL or more decreases HIV incidence by 51·6%, and this was the most cost-effective strategy for prevention of HIV infections at US$2960 per infection averted. Expansion of ART eligibility CD4 counts of 350-500 cells per μL is cost-effective at $900 per quality-adjusted life-year gained. Following health economic guidelines, expansion of ART use to individuals who have viral loads of more than 10 000 copies per mL among those with CD4 counts of more than 350 cells per μL was cost-effective to reduce HIV-related morbidity.

Interpretation: Our results show that province-wide home HTC every 5 years can be a cost-effective strategy to increase ART coverage and reduce HIV burden. Expanded ART initiation criteria that includes individuals with high viral load will improve the effectiveness of home HTC in linking individuals to ART who are at high risk of transmitting HIV, thereby preventing morbidity and onward transmission.

Funding: National Institutes of Health.

Figure 1. Model output for HIV prevalence and incidence

Model HIV prevalence (a) is similar to observed prevalence in KZN, and model HIV incidence (b) is similar to the average HIV incidence observed in KZN. Model output for prevalence (c) and incidence (d) for various intervention scenarios are shown with Baseline ART coverage of 36% for all HIV-positive persons (red). Home HTC with ART initiation at CD4≤350 cells/µL is shown in blue, home HTC with ART for persons with CD4>350 cells/µL and viral load>10,000 copies/mL is shown in green, and home HTC with ART initiation at CD4≤500 cells/µL is shown in purple.

Figure 2. Tornado diagram of one-way sensitivity analyses

We varied individual parameters one at a time while maintaining baseline values for other parameters in order to estimate their impact on the 10-year ICER per QALY gained of home HTC with ART initiation at CD4≤500 cells/µL. The Base Case ICER is $659 per QALY gained. *Multivariate analyses include variations in the cost of ART, cost of hospitalization, cost of Home HTC, and dropout from ART.