The push to use genotypic antiretroviral resistance testing (GART) for selecting meds gained support from several recent studies. In one, researchers compared outcomes of two groups of PWAs burdened with treatment failure: one whose drug histories and GART results were evaluated by experts who then recommended therapy choices (which the patients’ docs could accept or reject); the other in which the docs chose replacement meds based on antiretroviral experience alone. Two to three months later, the GART group had significantly lower viral loads. Although the effect of expert advice may partially account for the better outcome, most observers believe the results lend support to the notion of doing resistance testing when deciding on salvage therapy.
Another study found that in 17 people with failing Crixivan/AZT/3TC regimens, the viral isolates remained vulnerable to some drugs in the combo. In fact, no resistance to Crixivan was seen, whereas 14 out of 17 had virus that had mutated against 3TC. It may be that GART results can give information that allows for the removal of only the drugs that are failing rather than the whole regimen, potentially increasing future therapy options for many. In two other studies, GART data indicated the presence of virus resistant to one or more drugs in 21 to 28 percent of never-treated PWAs. These findings suggest that transmission of drug-resistant virus is much more frequent than previously suspected, and that using GART to guide initial drug choices might substantially improve outcomes.