Using data from Washington DC, one of the epicenters of the US HIV epidemic, we demonstrate that an intensive test and treat strategy can yield substantial benefits to individuals, improving HIV-infected life expectancy by up to 1.1 years compared to the current standard of care. Although most of the increase in life expectancy is achieved with improvements in testing frequency and coverage, an additional 4 months are likely added by ART initiation immediately upon diagnosis. And, compared to test and treat alone, further improvements in ART regimen efficacy may contribute an additional 7 months in life expectancy.
Beyond the clinical benefits to infected individuals, we find that test and treat
may have quantifiable population benefits. A test and treat
strategy may reduce overall life-years spent with transmissible HIV infection over the next 5 years by 15%. Any prevention intervention with the potential to decrease transmission by 15% and to produce substantial increases in individual HIV-infected life expectancy warrants further investigation. However, suggestions that a test and treat
strategy might be sufficient to eradicate the HIV epidemic create public expectations that cannot be realized [5
]. The transmission effect is the indirect result of viral suppression benefits that accrue most directly to the individual infected person. Therefore, prevention benefits result largely from earlier treatment initiation: providing ART upon diagnosis increases the number of transmissions averted over 5 years compared to frequent testing and guideline-concordant ART alone. Overall life-years with transmissible HIV RNA – and likely overall transmissions -- may be cut by almost one-quarter if test and treat
could be combined with major efforts to improve ART adherence and rates of virologic suppression. This analysis highlights the interplay of the components of test and treat
and their impact on HIV-infected individuals and the population. It also underscores that the success of any test and treat
strategy hinges upon the process of successfully making HIV test offers, completing tests, linking infected patients to care and maximizing the effects of ART [41
]. Numerous published programs that exemplify extraordinary efforts, testing large numbers of patients and identifying many new cases of HIV – even those beyond Washington DC -- have overall process success rates (from offer to acceptance to linkage to care) of only approximately 10% [29
]. These very low levels of participation will provide individual benefits to those identified, but will be inadequate to have a meaningful impact on the population. Although programs with extensive breadth (80% of the population offered) and depth (annual, or more frequent, testing), as illustrated by the optimistic scenario, may be challenging to achieve, such efforts could have a larger impact on population outcomes. Furthermore, improved ART efficacy -- likely attainable with currently available potent regimens, but beyond that even reported in trials -- is critical to effectively decrease transmission.
Like all model-based studies, this analysis is limited by the input data available. We derived input parameters from published sources, incorporating data from the Washington DC 2008 report whenever possible [1
]. In the optimized and idealized scenarios, we intended to portray a very high level of program and ART performance; the results demonstrate, even under such optimism, the anticipated magnitude of population benefit achievable from a test and treat
approach. To assess such population benefits, we report percent reduction in transmissible HIV RNA. The higher the initial HIV prevalence/incidence, the more the percent reduction translates into increased infections averted in absolute terms. The analysis of community viral load is restricted to prevalent and incident cases; to the extent that second- and third-generation HIV infections substantially contribute to community viral burden over a 5-year horizon, the benefits of test and treat
may have been underestimated. Data continue to emerge on the benefits and risks of ART at CD4 counts >350/μl. Although this model excludes the benefits (and/or risks) of early ART on “non-AIDS”-related morbidities, such as cardiovascular and renal disease, the input parameters reflect the toxicity profiles of current treatment and therefore likely underestimate the benefits from earlier ART [43
]. Natural history data used for this analysis may underestimate the proportion of hepatitis C co-infected patients in the urban DC population and thereby may over estimate HIV-infected life expectancy, in general [44
]. Finally, we have excluded costs from this analysis. Cost-effectiveness results, in order to be methodologically sound, must be reported on a population-wide scale. As such, these results are more speculative with regard to future transmissions and detract from the prevention message (rather than the economic one) that lies at the heart of current debate over test and treat
We find that dedicated efforts to address the HIV epidemic in Washington DC and in other heavily-affected US cities will substantially affect the survival of HIV-infected patients identified, averting many missed diagnoses and new AIDS cases. Moreover, earlier detection, linkage, and treatment of infected persons is likely to have a dramatic impact on secondary HIV transmission, reducing the number of new infections by as much as 15%. However, the success of such interventions hinges on careful attention to process and implementation – making frequent offers, securing high levels of consent, linking all detected cases to care, and initiating ART immediately. Even if future implementations greatly exceed the performance observed in recent, highly organized, well-financed programs, it is very unlikely that a test and treat strategy will stop the epidemic in Washington DC.