BACKGROUND: To end AIDS as a public threat by 2030, more innovative approaches are needed to identify undiagnosed people living with HIV (PLHIV) and expand access to HIV combination prevention for individuals at substantial risk of HIV acquisition. This study assessed the feasibility of using HIV-negative individuals at substantial risk of HIV acquisition as ‘index-clients’ to explore their sexual networks for HIV case-finding and scale up of PrEP uptake among HIV-negative, at-risk individuals in USAID DISCOVER-Health supported facilities in Zambia.
METHODS: The intervention was piloted in 32 project-supported sites in 2021 and 2022. HIV-negative PrEP clients were offered prevention index case testing to explore their sexual networks. All elicited individuals at substantial HIV acquisition risk were offered HIV index testing. Individuals testing positive for HIV were immediately offered antiretroviral therapy (ART); individuals testing negative were offered combination prevention services, including PrEP. Client-level data were recorded in registers from which key variables were derived for analysis using SPSS.
RESULTS: A total of 7,831 HIV-negative individuals, including 5,687 males aged 20-40 years and 2,144 females aged 18-35 years were offered reverse index testing within the study period. From these, 5,653 sexual network contacts were elicited. Females constituted the smallest proportion of elicited contacts at 1,357 (24%). Females were two times more likely to accept HIV testing than males (OR=2.47; 95% CI 2.18-2.81, p<0.001) and were twice as likely to test positive for HIV than males (OR=2.08; 95% CI 1.46-2.96). Additionally, 128 (3.7%) HIV-positive contacts were identified, comprising 75 (59%) males and 53 (41%) females, all of whom were linked to ART. Over 3,300 HIV-negative sexual contacts (93%) were linked to PrEP. Females were more likely to initiate PrEP than males (89% vs. 83%) (OR=1.62; 95% CI 1.28-2.05).
CONCLUSIONS: Prevention index testing may increase the identification of HIV-negative individuals at substantial risk of HIV acquisition with spillover benefits of finding undiagnosed PLHIV for scaling up linkage to combination prevention services and ART, respectively. Further implementation and research is needed to assess the impact of this approach in high HIV risk populations.

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