HIV This Week

Examining the promise of HIV elimination by 'test and treat' in hyperendemic settings.

Dodd PJ, Garnett GP, Hallett TB. AIDS. 2010 Feb 11. [Epub ahead of print]

It has been suggested that a new strategy for HIV prevention, 'Universal Test and Treat', whereby everyone is tested for HIV once a year and treated immediately with antiretroviral therapy if they are infected, could 'eliminate' the epidemic and reduce antiretroviral therapy costs in the long term. The authors investigated the impact of test-and-treat interventions under a variety of assumptions about the epidemic using a deterministic mathematical model. Their model shows that such an intervention can substantially reduce HIV transmission, but that impact depends crucially on the epidemiological context; in some situations, less aggressive interventions achieve the same results, whereas in others, the proposed intervention reduces HIV by much less. It follows that testing every year and treating immediately is not necessarily the most cost-efficient strategy. Dodd and colleagues also show that a test-and-treat intervention that does not reach full implementation or coverage could, perversely, increase long-term antiretroviral therapy costs. Interventions that prevent new infections through antiretroviral therapy scale-up may hold substantial promise. However, as plans move forward, careful consideration should be given to the nature of the epidemic and the potential for perverse outcomes.

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Editors’ note: This modelling analysis highlights three important aspects of ‘test and treat’ strategies that require thoughtful consideration. The first is epidemic context and, in particular, the properties of the sex partner network (heterogeneity, concurrency, and mixing) that can influence the impact of a ‘test and treat’ approach. The second is the diminishing returns of yearly testing – this modelling suggests that testing everyone every 3 to 5 years appears most cost-efficient, depending on the epidemic context, life expectancy, and the costs of testing and treatment. The third is the dramatic spiralling in treatment costs that is likely if testing is not frequent enough and treatment coverage is suboptimal. These qualitative insights are helpful and they show that we need more evidence to inform the modelling. There is no doubt that the science underpinning ‘test and treat’ is promising: viral load drops in individuals placed on antiretroviral treatment and reduced transmission in discordant couple studies. Policy makers need the results of clinical trials, such as HPTN 052, and community impact evaluations such as the British Columbia Seek and Treat pilot project and the NIH Test and Treat feasibility assessments in Washington and the Bronx, to inform policy and programming. In the meantime, millions of people in need of treatment now, whether defined by the old under 200 CD4+ count criterion or the new under 350 CD4+ cell count guidelines, will die if we don’t get treatment to them urgently.