HIV resistance: frequency, testing, mechanisms.

Recent data suggest that the prevalence of drug-resistant HIV in newly diagnosed patients may have leveled off at approximately 10% over the past several years. Further, there is some indication that the rates of emergence of resistance during long-term treatment have decreased in recent years with optimization of antiretroviral therapy. The importance of initial resistance testing is emphasized by findings indicating markedly increased risk of treatment failure in patients with resistance mutations at baseline. Genotypic and phenotypic testing are each associated with advantages and disadvantages in initial and subsequent resistance testing. Data on resistance patterns for new drugs and new drug classes are beginning to emerge. This article summarizes a presentation on HIV resistance made by Daniel R. Kuritzkes, MD, at an International AIDS Society-USA Continuing Medical Education course in San Francisco in May 2007.