"Even after the harmful consequences of combination antiretroviral therapy were incorporated into our model, earlier treatment was still favoured for many scenarios that we evaluated," Dr R. Scott Braithwaite, at Yale University in West Haven, Connecticut, and colleagues report.
Specifically, their computer simulation model suggests that starting anti-HIV therapy once the number of CD4 cells drops to 500 cells per microlitre of blood - rather than at lower levels recommended by current guidelines - would be beneficial.
Doctors use CD4 cell counts to gauge the function of the immune system. As levels of these cells decline, so does the ability of the patient's immune system to function.
Earlier the better
For 30-year-olds, the researchers found that earlier initiation of combination antiretroviral therapy was "always preferred" regardless of the amount of virus circulating in the body because the risks (increase in death from drug toxicity, increase in accumulation of resistance mutations, and decrease in future drug options) were small compared with the benefit (decrease in HIV-related death from the effect of therapy on the natural history of HIV).
The computer simulation showed that 40-year-old patients would benefit from therapy started at a CD4 count of 500 when their viral load (the amount of HIV circulating in the body) exceeds 100 000 copies of the virus per millilitre of blood.
For 50-year-olds, the risk of toxic side effects of antiretroviral therapy outweighed the benefits of early treatment. "Our findings may affect clinical care because they provide evidence in favour of treatment in several settings in which clinical guidelines are ambiguous," Braithwaite and colleagues note, "increasing life expectancy by as much as 2.8 years." – (ReutersHealth) - (February 2008)