Abstract

AIDS: An overview of genotypic and phenotypic drug-resistance assays, or tests, are described. Genotypic assays identify changes in the sequence of nucleotide bases in HIV by detecting amino acid substitutions. Genotypic tests can only discern mutations already identified by researchers, and must be conducted on individuals whose viral load is a minimum of 500 copies. More sensitive tests should be available by the end of 1999. Phenotypic tests assess the ability of HIV to replicate when exposed to particular drugs, and may help researchers identify the necessary quantity of a drug to halt reproduction. Also discussed are HIV subpopulations which are often not detected by the assays, and may be resistant to certain drugs. Two clinical trials are cited, GART (Genotypic Antiretroviral Resistance Testing) and VIRADAPT, which observed benefits from conducting genotypic testing. A glossary of terms used in the article is provided.