An often-referenced concept in current conversations about our efforts to address HIV/AIDS in the United States is the so-called "treatment cascade". This concept is a model being used by Federal, state and local agencies to identify issues and opportunities related to improving the delivery of services to persons living with HIV across the entire continuum of care -- from diagnosis of HIV infection and active linkage in care to initiation of antiretroviral therapy (ART), retention in care, and eventual viral suppression -- meaning no detectable virus in the blood. The treatment cascade is bound to be a topic of discussion at the XIX International AIDS Conference (AIDS 2012) next week, so we wanted to offer followers of this blog a primer.
What Is the HIV/AIDS Treatment Cascade?
The HIV/AIDS treatment cascade is a way to show, in visual form, the numbers of individuals living with HIV/AIDS who are actually receiving the full benefits of the medical care and treatment they need.
This model was first described by Dr. Edward Gardner and colleagues, who reviewed current HIV/AIDS research and developed estimates of how many individuals with HIV in the U.S. are engaged at various steps in the continuum of care from diagnosis through viral suppression. Their analysis, published in the March 2011 edition of the journal Clinical Infectious Diseases, found that along each step of the cascade, a significant number of people living with HIV in the U.S. "fall off", and only a minority of persons with HIV actually achieve suppression of their viral infection.
Subsequently, in late 2011 CDC did its own analysis of HIV surveillance datasets, viral load and CD4 laboratory reports, and other published data to develop national estimates of the number of HIV-infected persons at each step of the treatment cascade. Their findings, published in CDC's Morbidity and Mortality Weekly Report (MMWR), were similar to those of Dr. Gardner and his colleagues and can be summarized as follows:
For every 100 individuals living with HIV in the United States, it is estimated that:
- 80 are aware of their HIV status.
- 62 have been linked to HIV care.
- 41 stay in HIV care.
- 36 get antiretroviral therapy (ART).
- 28 are able to adhere to their treatment and sustain undetectable viral loads.
In short, CDC estimated that only 28 percent of the more than 1 million individuals in the U.S. who are living with HIV/AIDS are getting the full benefits of the treatment they need to manage their disease and keep the virus under control. Put another way, nearly 3 out of 4 people living with HIV in the U.S. have failed to successfully navigate the treatment cascade.
Since a picture "is worth a thousand words," consider this representation from a new CDC fact sheet on Today's HIV Epidemic in the U.S.:
[For more information on the treatment cascade, read CDC's Vital Signs brief on the treatment cascade and the related MMWR reviewing their own analysis of the proportion of Americans living with HIV at each step in the cascade.]
Why Is the HIV/AIDS Treatment Cascade Important?
The HIV/AIDS treatment cascade provides a way to examine critical questions, including: How many individuals living with HIV are getting tested and diagnosed? Of those, how many are linked to medical care? Of those, how many are retained in care? Of those, how many receive ART? Of those, how many are able to adhere to their treatment plan and achieve viral suppression? By closely examining these separate steps, policymakers and service providers are able to pinpoint where gaps may exist in connecting individuals living with HIV/AIDS to sustained, quality care. Knowing where the drop-offs are most pronounced, and for what populations, helps national, state and local policymakers and service providers to implement system improvements and service enhancements that better support individuals as they move from one step in the continuum to the next.
Reducing these drop offs across the continuum of HIV care is vitally important because:
- Lowering the amount of virus in the body can keep a person with HIV healthy longer.
- Keeping the virus under control (namely, an "undetectable viral load") greatly lowers the chances of passing HIV on to others.
- More than 18,000 people with AIDS die each year. The number of people with HIV who get AIDS has decreased over time because of advances in medical care and ART. Still, without treatment, most persons with HIV develop AIDS within 10 years of infection, which results in substantial morbidity and premature death.
As colleagues at the CDC have noted, to meet the goals of the National HIV/AIDS Strategy and break the cycle of HIV transmission in the United States we must achieve high levels of engagement at every stage in the continuum.
How Is the HIV/AIDS Treatment Cascade Being Used?
At the Federal level, government agencies use the treatment cascade to inform discussions about how best to prioritize and target resources. For example, the treatment cascade points to the importance of continuing to support the adoption of routine HIV testing of all adults and adolescents in medical care settings, as was first recommended by the CDC in 2006. Simply stated, we won't be able to link more individuals with HIV/AIDS into care if we can't diagnose them!
At the State and local levels, program planners also apply the treatment cascade -- using local data -- to assess where resources are needed and then to target them accordingly. For example, the Los Angeles County Department of Public Health produced a program brief summarizing data on the spectrum of engagement in care and treatment for all persons infected with HIV in LA County. Similar analysis has been done in San Francisco, Chicago, Washington, DC and other communities, enabling them to take steps to improve engagement at each step in the continuum of HIV care.
In later posts, we will feature more examples of how various partners are using the treatment cascade to assess and improve HIV programs and services. In the meantime, how are you using the treatment cascade or what are your ideas about how it could be used to achieve the goals of the NHAS? What interventions are needed to address the social factors that interfere with active linkage and retention in care? Share your ideas in the Comments section below.
Ensuring success at each step in the HIV treatment cascade will move us closer to achieving the vision of the National HIV/AIDS Strategy.
Ronald Valdiserri, M.D., M.P.H., is deputy assistant secretary for health, infectious diseases, and director of the Office of HIV/AIDS Policy at the U.S. Department of Health and Human Services.