Role of HIV phenotypic assays in the management of HIV infection.

Contemporary phenotypic assays such as the PhenoSense HIV assay are more straightforward to interpret than genotyping results because they do not require the expert interpretation of complex mutation patterns. The drug susceptibility data provides information for the clinician to select a treatment regimen effective against the predominant viral population circulating in the patient's blood. Compared to traditional phenotypic assays, the PhenoSense HIV assay uses a virus vector and a luciferase reporter gene to provide a quick and sensitive measure of viral replication. The main use of phenotypic assays at present is to identify those antiretroviral drugs that still retain activity against the patient's virus. Phenotypic assays are useful to provide guidance after treatment failure and to select a proper combination of drugs prior to initiation of therapy. They are also useful to detect transmission of resistance virus and to monitor HIV patients during early viral rebound. In essence, phenotypic testing provides information to target antiretroviral therapy against the predominant HIV variant in the patient for a prolonged suppression of viral replication, decreased mortality, and lower health-care costs.