HIV ‘test and treat’ strategy could have individual and public health benefits in Washington DC

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 15^th 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.”