Human immunodeficiency virus drug resistance testing: state of the art in genotypic and phenotypic testing of antiretrovirals.

Antiretroviral drugs have significantly reduced death rates from the acquired immunodeficiency syndrome in the United States. They are highly effective in reducing viral replication, but their utility is threatened by rapid development of drug resistance. Although antiretroviral drug resistance testing is available by either genotyping or phenotyping, no consensus guidelines have been published regarding the appropriate use or interpretation of these new tests. Even though their role in clinical practice is not defined, it is important for clinicians to become familiar with relative advantages and disadvantages of genotypic and phenotypic testing and various mechanisms of antiretroviral resistance.