The adoption of an HIV “test and treat”
strategy in the US capital, Washington DC, could have significant individual
and public health benefits, investigators argue in the August
15th edition of Clinical Infectious
Diseases. Such a policy could add over a year to the average
life-expectancy of an HIV-positive patient, and reduce the onward HIV transmissions
by 15% over five years.
But the researchers caution that it is
highly unlikely that a test and treat approach would only be able to eliminate
HIV transmissions. Such an outcome would only be achievable if there was
universal monthly testing, 100% linkage to care, with all patients commencing
immediate antiretroviral therapy and having excellent outcomes.
Washington DC has an adult prevalence of
diagnosed HIV of 3%. In addition, it is estimated that a further 20% of HIV
infections in the city are undiagnosed.
Late diagnosis of HIV is an important
factor underlying much of the continued AIDS-related illness and death seen in
richer countries. Moreover, some research suggests that undiagnosed individuals
are the main source of onward HIV transmissions.
Treatment with antiretroviral drugs can
mean that many HIV-positive individuals have a good chance of having a
near-normal prognosis. An additional benefit of HIV treatment is that it
substantially reduces the risk of onward transmission of the virus.
Because of these benefits a number of
health authorities have adopted so-called test and treat policies. These
involve routine adult HIV testing and expanding the number of patients treated
with antiretroviral drugs. Funding was
recently secured for a two-year pilot test and treat programme in the US
capital.
Investigators used a mathematical model to
calculate the likely benefits of such an approach compared to current practice
in the city.
They defined current practice as no routine
HIV testing and the initiation of antiretroviral therapy when an individual’s
CD4 cell count was below 350 cells/mm3.
A test and treat strategy was defined as
annual HIV testing and immediate antiretroviral therapy.
Based on the current epidemic and HIV
testing practices, the model assumed that the prevalence of undiagnosed HIV was
0.6%, that annual HIV incidence rate was 0.13%, that 31% of patients would be
offered an HIV test, that 60% would accept screening, and that 50% of patients
would be linked to care.
Currently, the mean age of the population
in Washington D.C. is 41 years, and the mean CD4 cell count in individuals with
undiagnosed HIV infection is estimated to be 262
cells/mm3.
The investigators calculated that annual
HIV testing and the initiation of antiretroviral therapy at the time of
diagnosis would significantly increase the life expectancy of those diagnosed
with the infection.
In the context of the current screening and
treatment strategy, a 41 year old diagnosed with HIV was estimated by the researchers
to have an additional life expectancy of 23.9 years.
Annual testing and immediate HIV therapy
increased this to 25 years.
However, the investigators think that this
is an underestimate, as their model did not take into account likely improvements
in HIV treatment and care in the future.
A test and treat strategy was also shown to
have public health benefits. The investigators calculated that such an approach
would reduce the amount of time patients had a transmissible viral load (above
500 copies/ml) by 15% over five years, therefore averting 15% of incident HIV
infections.
But they caution that increasing the number
of patients diagnosed and taking treatment will not, realistically, halt the
epidemic.
They write, “near elimination of the HIV-infected
population with transmissible viral load is achieved with monthly HIV
screening, 100% program participation and linkage to care, and perfectly
suppressive and durable ART [antiretroviral therapy] efficacy.”
“We find”, conclude the investigators”,
that dedicated efforts to address the HIV epidemic in Washington DC and in
other heavily affected United States cities will substantially affect the
survival of HIV-infected patients identified”.
They continue, “earlier detection, linkage, and treatment…is likely to
have a dramatic impact on secondary HIV transmission.” But they caution that,
“it is very unlikely that a test and treat strategy will stop the epidemic in
Washington DC.”