How do different eligibility guidelines for antiretroviral therapy affect the cost-effectiveness of routine viral load testing in sub-Saharan Africa?

Abstract

Background: Increased eligibility guidelines of antiretroviral therapy (ART) may lead to greater routine viral load monitoring. However, in resource-constrained settings, the additional resources required by greater routine viral load monitoring may impair ability to comply with expanded eligibility guidelines for ART.

Objective: We use a published validated computer simulation of the HIV epidemic in East African countries (expanded to include transmission as well as disease progression) to evaluate the cost-effectiveness of routine viral load monitoring.

Methods: We explored alternative scenarios regarding cost, frequency, and switching threshold of routine viral load monitoring (including every 6 or every 12 months; and switching thresholds of 1000, or 10 000 copies/ml), as well as alternative scenarios regarding ART initiation (200, 350, 500 cells/μl, and no CD4 cell threshold). For each ART initiation strategy, we sought to identify the viral load monitoring strategy at which the incremental cost-effectiveness ratio (ICER) of more frequent routine viral load testing became more favorable than the ICER of more expansive ART eligibility. Cost inputs were based on data provided by the Academic Model Providing Access to Healthcare (AMPATH), and disease progression inputs were based on prior published work. We used a discount rate of 3%, a time horizon of 20 years, and a payer perspective.

Results: Across a wide range of scenarios, and even when considering the beneficial effect of virological monitoring at reducing HIV transmission, earlier ART initiation conferred far greater health benefits for resources spent than routine virological testing, with ICERs of approximately $1000 to $2000 for earlier ART initiation, versus ICERs of approximately $5000 to $25 000 for routine virological monitoring. ICERs of viral load testing were insensitive to the cost of the viral load test, because most of the costs originated from the downstream higher costs of later regimens. ICERs of viral load testing were very sensitive to the relative cost of second-line compared with first-line regimens, assuming favorable value when the costs of these regimens were equal.

Conclusion: If all HIV patients are not yet treated with ART starting at 500 cells/μl and costs of second regimens remain substantially more expensive than first-line regimens, resources would buy more population health if they are spent on earlier ART rather than being spent on routine virological testing.

Fig. 1. Schematic of computer simulation

The progression module provides data to inform the transmission module. Additionally, there are important simulation features that are not depicted in the diagram. The probability of transmission is higher from men to women, and lower from women to men. Additionally, mixing may be asymmetric by age (greater from older men to younger women; lower from younger men to older women). Although similarly sized cubes are used to designate different states of the simulation, this is not meant to suggest that the number of individuals in each state is similar: the proportion may vary from state to state, and may also vary between corresponding states of men and women. 1° HIV, primary HIV infection.

Fig. 2. Efficient frontiers comparing benefits of earlier antiretroviral therapy and more aggressive laboratory monitoring

(a) Considering progression alone and (b) considering transmission as well as progression. Note that (a) models only HIV-infected persons and shows mean per-person costs and QALYs, whereas (b) models all persons, regardless of HIV infection, and shows total population costs and ART, antiretroviral therapy; VL, viral load.

Fig. 2. Efficient frontiers comparing benefits of earlier antiretroviral therapy and more aggressive laboratory monitoring

(a) Considering progression alone and (b) considering transmission as well as progression. Note that (a) models only HIV-infected persons and shows mean per-person costs and QALYs, whereas (b) models all persons, regardless of HIV infection, and shows total population costs and ART, antiretroviral therapy; VL, viral load.