For three decades, Mathematica has partnered with the HIV/AIDS Bureau in the Health Resources and Services Administration (HRSA) on research projects to evaluate in a way that would help improve the performance of the Ryan White HIV/AIDS Program (RWHAP). The RWHAP serves more than half of the 1.2 million people with diagnosed HIV in the United States. With an annual budget of more than $2 billion, the program is the third-largest source of public financing of HIV care and treatment in the United States.
Two papers from a recently completed study for HRSA that were published in the Journal of Acquired Immune Deficiency Syndromes present the findings on the long-term economic and public health impact of the RWHAP. The findings highlight the important role that the RWHAP plays in the United States’ public health response to the HIV epidemic. The first paper describes and presents the validation results for an agent-based microsimulation model used to estimate the cost-effectiveness of the program. The second paper presents the results from the model, focusing on the total lifetime costs of care, number of HIV infections and deaths averted, and number of quality-adjusted life years gained over a 50-year horizon. The paper also estimates an incremental cost-effectiveness ratio (ICER) for the program.
“Agent-based modeling techniques are ideally suited for modeling the spread of pathogens such as HIV/AIDS, as they account for and focus on the interactions among individuals. This type of modeling work offers a flexible approach to assessing the long-term health outcomes and costs of this comprehensive system of HIV care and treatment,” said Ravi Goyal, lead author of the papers.
Developing and validating the agent-based model
The RWHAP represents a large, multifaceted HIV care delivery system rather than a single intervention. The scope of the program required the researchers to devise creative solutions to several unique challenges, such as determining which services to include in the model, estimating the impact of those services on care retention and viral suppression, quantifying the need for and receipt of such services with and without the RWHAP, and measuring the cost of those services.
The agent-based model was designed to reflect the current overall HIV epidemic in the United States. The model simulates an individual’s progression along the HIV care continuum, from undiagnosed to diagnosed, to care and treatment, to viral suppression. It also allows an individual to drop out of care and to reengage with care. The model simulates HIV transmission using two network-based mechanisms: injection drug use and sexual contact. To test the validity of the innovative model, the researchers projected HIV incidence, mortality, life expectancy, and lifetime care costs over 5 and 10 years and compared the results with external benchmarks.
Assessing cost-effectiveness of the RWHAP
Using the newly developed agent-based model, the researchers estimated health care costs and outcomes over 50 years with the RWHAP relative to the costs and outcomes expected to prevail if the medical and support services funded by RWHAP were not available. The researchers made three key assumptions that likely underestimate the cost-effectiveness of the program: first, that in the absence of the RWHAP, only uninsured clients would lose access to the outpatient medical and support services for their disease; second, people eligible for the RWHAP have the same chance of entering care and treatment as those who are not; and third, the need for services is the same in both systems of care.
The study found that, compared with a scenario without the RWHAP, over the next 50 years, the program will result in the following:
- 38 percent increase in the proportion of people in HIV care and treatment
- 44 percent increase in the proportion of people whose HIV disease is virally suppressed
- 18 percent decrease in the number of new HIV infections
- 31 percent decrease in the number of deaths among people with HIV
- 2.7 percent increase in the number of quality-adjusted life years among people with HIV
- 25 percent increase in total health care costs for people with HIV
Based on results of the model, compared with the non-RWHAP scenario, the RWHAP is estimated to have an ICER of $29,573 per quality-adjusted life year gained. The program’s ICER is well within the threshold established by the World Health Organization for being very cost-effective and compares favorably to other U.S.-based HIV care and treatment interventions.
