Improved Indicators for Subnational Unmet Antiretroviral Therapy Need in the Health System: Updates to the Naomi Model in 2023

Abstract

Background: Quantifying subnational need for antiretroviral therapy (ART) for HIV is challenging because people living with HIV (PLHIV) access health facilities in areas that may differ from their residence. We defined and demonstrated new indicators for PLHIV treatment needed to guide health system target setting and resource allocation.

Setting: Botswana.

Methods: We extended Naomi, a Bayesian small-area model for estimating district-level HIV indicators from national household survey and HIV service delivery data. We used model outputs for ART seeking probabilities in neighboring districts to define the "PLHIV (attending)" indicator representing the estimated number of PLHIV who would seek treatment at health facilities in a district, and "Untreated PLHIV attending" representing gaps in ART service provision. Botswana 2021 district HIV estimates were used to demonstrate new outputs and assess the sensitivity to uncertainty in district population sizes.

Results: Across districts of Botswana, estimated adult ART coverage in December 2021 ranged 90%-96%. In the capital city Gaborone, there were 50,400 resident PLHIV and 64,200 receiving ART, of whom 24% (95% CI: 20 to 32) were estimated to reside in neighboring districts. Applying ART attendance probabilities gave a "PLHIV attending" denominator of 68,300 and unmet treatment need of 4100 adults (95% CI: 3000 to 5500) for Gaborone health facilities. The facility-based "PLHIV attending" denominator was less-sensitive to fluctuations in district population size assumptions.

Conclusions: New indicators provided more consistent targets for HIV service provision, but are limited by ART data quality. This challenge will increase as treatment coverage reaches high levels and treatment gaps are smaller.

FIGURE 1.

Estimates of Naomi key HIV indicators for Botswana in December 2021 Health district estimate (A) HIV prevalence and (B) ART coverage for adults aged 15–49 by September 2021.

FIGURE 2.

Health district ART coverage for December 2021 among resident PLHIV compared to ratio of reported ART clients at health facilities relative to estimated PLHIV for all districts (A) and in 4 districts in south-eastern Botswana neighboring the capital city Gaborone (B + C).

FIGURE 3.

ART attending dynamics for Gaborone and neighbors. A, Targets of unmet need using resident PLHIV vs. B, All PLHIV eligible for treatment in a district catchment area and (C) Distribution of ART clients attending ART services in home districts and in neighboring districts.

FIGURE 4.

Sensitivity of district-level PLHIV indicators to fluctuations in overall population denominators. Results from 1000 simulations using randomly adjusted district population estimates.