Only 19% of HIV-positive individuals in the US have an
undetectable viral load, and this means that a “test-and-treat” strategy by
itself will not be enough to control the country’s HIV epidemic, investigators
argue in the March 15th edition of Clinical Infectious Diseases.
Late diagnosis, low levels of referral and retention in
specialist HIV care, and sub-optimal adherence to antiretroviral therapy all
undermined the potential for test-and-treat to eradicate transmission of the
“This review demonstrates that incomplete engagement in HIV
care is common in the United States and that incompletely engaged individuals
account for the largest proportion of HIV-infected individuals with detectable
viremia,” comment the investigators, who believe their findings “have direct
implications for test-and-treat programs, because disengaged individuals
continue to contribute to the ongoing transmission of HIV infection.”
The investigators also estimated that even in the best-case
scenarios over a third of HIV-positive individuals in the US would still have a
detectable viral load and therefore be at risk of transmitting the virus to
Prof. Joep Lange in his accompanying editorial described the
small proportion of US patients with an undetectable viral load as “shocking.”
He argued that “combination prevention” was the best hope of controlling the
Improvements in HIV treatment and care mean that many
HIV-positive patients now have a realistic hope of a normal prognosis. To have
the best hope of this outcome individuals need to have their infection
diagnosed early, utilise specialist HIV care services, initiate antiretroviral
therapy at the optimum time, and have high levels of adherence to their
Another advantage of antiretroviral therapy is its impact on
infectiousness. Patients who have an undetectable viral load when taking HIV
treatment are at very low risk of transmitting the virus to others. Therefore,
a test-and-treat strategy has been advocated as a way of not only improving the
life-expectancy of patients already infected with the virus, but also as a way
of controlling the epidemic.
Investigators from the US wished to see if this approach to
prevention was realistic.
There are approximately 1.1 million HIV-infected individuals
in the US, and HIV incidence in the country is steady at around 56,000 new
infections each year.
Rates of HIV testing in the US have increased in recent
year, but approximately a fifth of all infections are still undiagnosed. The
investigators note that undiagnosed individuals “cannot engage in treatment
that reduces morbidity and mortality, may participate more often in high-risk
HIV transmission behavior, and have a higher risk of transmitting HIV to others
than do those who are aware of their HIV infection.”
Failure to link patients with specialist care after their
diagnosis is also common. The investigators found that 25% of newly-diagnosed
individuals were not successfully linked to HIV care within six-twelve months
of their diagnosis, and between 10%-20% of patients remained unengaged in care
three to five years after their diagnosis.
Rates of retention in care were also found to be far from
perfect. “50% of known HIV-infected individuals are not engaged in regular HIV
care,” comment the investigators, adding “poor engagement in care is associated
with poor health outcomes, including increased mortality. In addition, these
individuals contribute to ongoing transmission in the community.”
But being in care did not guarantee that patients would
receive optimum therapy. The investigators calculated that on the basis of
current guidelines, 80% of in-care patients were eligible for antiretroviral
therapy. However, approximately 27% of individuals either declined this
treatment or failed to initiate it for some other reason.
Moreover, results from cohort studies suggest that between
4% - 6% of patients stop taking their HIV therapy each year.
Newer anti-HIV drugs are powerful, have generally mild
side-effect profiles, and forgiving adherence requirements. Nevertheless, the
researchers found that between 13% - 22% of patients taking antiretroviral
therapy still have a detectable viral load and are at risk of transmitting the
virus to others.
After taking into account all these factors the
investigators calculated that only 210,000 HIV-positive patients in the US have
an undetectable viral load. These patients constitute just 19% of the
HIV-infected population in the US.
“With > 80% of HIV-infected individuals in the United
States having detectable HIV viremia, it is not surprising that the incidence
of HIV infection has not decreased in the United States despite almost 15 years
of widespread access to antiretroviral therapy,” comment the investigators.
However, they also found that even in a best-case scenario,
a test-and-treat strategy would not be sufficient to control the HIV epidemic.
They write: “Diagnosis of 90% of HIV infections, achievement
of 90% engagement in care, treatment of 90% of engaged individuals, and
suppression of viremia in 90% of treated individuals could lead to considerable
improvements in the proportion of HIV-infected individuals in the United States
with undetectable viral loads. However, even in this ideal scenario,
approximately 34% of HIV-infected individuals will remain viremic, with the
potential to spread HIV infection to others.”
The researchers therefore conclude, “complete eradication of
HIV infection through test-and-treat programs is unlikely.”
Nevertheless, they believe that “incremental improvements in
methods to overcome the greatest care challenges today in the United States –
undiagnosed HIV infection and inadequate engagement in HIV care – will improve
the care of HIV-infected populations and decrease the incidence of HIV
infection in the future.”
In his accompanying editorial, Prof. Lange suggests that the
study shows the limitations of a test-and-treat approach.
He writes: “It is unlikely that ‘test and treat’ strategies
by themselves, even if vigorously and comprehensively pursued, will be
sufficient to end the epidemic. It should be clear that ‘combination HIV
prevention’, using a mix of available prevention tools, including ‘test and
treat’ strategies, in a context-specific manner based on knowledge about local,
national, and regional epidemics, is the way forward.”