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Questioning Test and Treat

The discussion about test and treat has picked up steam over the past few years. First because of mathematical models that show this strategy, which calls for universal HIV testing and immediate treatment for all those infected, could dramatically decrease HIV incidence.

 

However, today in Vienna, two speakers took issue with the mathematical modeling that serves as the basis for using treatment as prevention. Myron Cohen of the University of North Carolina said that depending on the assumption you use in the model, you could show that test and treat can elimiate the epidemic or actually make it worse.

In this morning’s plenary session, Bernard Hirschel of the University of Geneva said, “Let’s declare a model armistice and instead get some data.” This was Cohen’s plea as well. “We need to provide data that proves or disproves these assumptions.” Some studies of the test and treat strategy are already underway, while others, including a large clustered clinical trial outlined by Hirschel, are still in the planning stages.

Test and treat has also picked up momentum based on the results of some observational studies that have shown that the number of HIV diagnoses in certain cities or communities has dropped at the same time that there was an increased uptake of highly active antiretroviral therapy. But Cohen pointed out that while three observational studies have shown a correlation between ARV use and a declining number of HIV diagnoses, there are also three studies that have found no effect.

Cohen also questioned whether the prevention benefit of antiretroviral treatment will be durable. Earlier this year at the Conference on Retroviruses and Opportunistic Infections, a study showed that impressive protection against HIV transmission among discordant couples when the infected partner was on treatment. But Cohen said this study followed couples for a short period of time. He also previewed a presentation in Vienna tomorrow by researchers from the Chinese Center for Disease Control that shows that in a cohort of discordant couples they studied there was no difference in HIV transmission rates when the infected partner was on therapy.

Another question is just how a test and treat approach would be financed, given that 60% of the people in need (those with CD4+ T cell counts below 350) still don’t have access to antiretroviral therapy. Mathematical modelling, although it has obvious caveats, has shown that prioritizing treatment for these individuals will have a greater impact on reducing HIV incidence than a unviersal test and treat strategy. The question of funding for test and treat hasn’t been addressed directly at this conference, but funding questions have been omnipresent. Whether it's talk about the upcoming replenishment of the Global Fund, the failure of US President Obama to increase PEPFAR funding, or the need for more innovative financing approaches, it seems that apart from the first microbicide success, money may be the biggest story of AIDS 2010.