'Test-and-treat' is unlikely to be an effective strategy to control the HIV epidemic in the United States without improvements in retention in care, investigators argue in the online edition of Clinical Infectious Diseases. A mathematical model suggested that without interventions to address poor levels of engagement in HIV care, there could be as many as 1.39 million new HIV infections in the US over the next 20 years, at a cost of $256 billion. Targeting testing and linkage would only prevent 21% of these new infections. But a package of interventions comprising testing, linkage and retention in care would prevent over half of the projected new infections, reduce AIDS-related mortality by almost two-thirds and be cost effective.
“To alter the course of the HIV epidemic in the United States, strategies of ‘test and treat’ alone may be insufficient; attention to the full continuum of care will be essential,” comment the authors.
United States guidelines recommend expanded HIV testing and antiretroviral therapy at any CD4 count as strategies to reduce rates of AIDS-related deaths and HIV transmissions. However, this approach may not be as effective as hoped. Recent research has shown that there is significant attrition at each stage of the HIV care continuum in the US. Up to a fifth of HIV-infected individuals are undiagnosed; 20% of recently diagnosed patients are not linked to care within 90 days; 54% of patients are not retained in care; only 30% of diagnosed patients have an undetectable viral load.
A team of investigators wanted to assess the epidemiological and economic impact of various strategies to increase testing rates, linkage to care and retention in care.
They therefore developed a model that projected the course of the United States’ HIV epidemic over 20 years. Their baseline scenario assumed current levels of testing and engagement with care. They then modelled the likely impact of several other interventions:
Enhanced targeted screening of high-risk individuals.
Increased rates of targeted and generalised HIV testing.
Increased linkage to care – boosting the level of newly diagnosed patients completing an HIV care visit within three months from current levels to 70%.
Improved retention in care – 50% reduction each year in rate of dropping out of care plus a 50% increase in yearly rate of patients returning to care.
The investigators modelled the impact of each strategy in terms of the prevention of new infections and AIDS-related deaths, total costs and cost effectiveness (quality-adjusted life years – QALYS).
The baseline model – HIV therapy at any CD4 count and current levels of engagement with care – would result in 1.39 million new infections over 20 years, with 435,000 AIDS-related deaths. The estimated cost to the US health system would be $256 billion.
Strategies that focused on increasing testing had only modest benefits. Targeting high-risk groups would prevent 215,000 new infections (16% reduction) at a cost of £49 billion, approximately $85,000 per QALY-gained. Screening the entire population every three years would only prevent 11,600 additional new infections and would require an additional $22 billion of funding.
Increased levels of testing would prevent between 18%-21% of projected AIDS-related deaths.
Enhancing the proportion of patients linked to care within 90 days of diagnosis combined with higher levels of testing of high-risk individuals would avert 292,000 projected infections (21% reduction). The estimated cost to the US health system would be $53 billion, or approximately $66,000 per QALY gained.
The investigators’ model showed that increasing levels of ongoing engagement with care was likely to be a much more effective strategy, averting 494,000 projected infections (36% reduction) at a cost of $33,700 per QALY gained.
More effective still was a combined package of interventions that included screening of high-risk groups, improved linkage, and enhanced retention and re-engagement with care. The authors estimated this would prevent 752,000 (54%) of the projected new infections and 64% of AIDS-related deaths. The cost of this strategy would be $96 billion, a little over $46,000 per QALY-gained.
“Although targeted HIV screening, rapid linkage to care, and early ART initiation are all effective interventions,” conclude the authors, “improved retention may ultimately have a more transformative impact on the HIV epidemic in the US over the next 20 years.”
The study is praised as “excellent” in an accompanying editorial.
Shah M et al. The epidemiological and economic impact of improving HIV testing, linkage, and retention in care in the United States. Clin Infect Dis, online edition, 2015.
Gardner EM. Improving retention in HIV care: a cost-effective strategy to turn the tide on HIV and AIDS in the United States. Clin Infect Dis, online edition, 2015.