Update on antiretroviral drug resistance testing: combining laboratory technology with patient care.

HIV drug resistance testing has been considered an emerging asset to modernized HIV management. Despite the increased number of antiretroviral agents currently available, virologic failure remains a significant problem. Drug resistance testing is designed to identify gene mutations or viral growth characteristics that suggest reduced drug susceptibility. The widespread use and virologic benefits of resistance testing in some prospective clinical trials have prompted the development of formal guidelines by expert panels for clinical use. Despite technological advances in drug resistance testing, clarification of assay interpretation, assay standardization, and the results from validation studies are needed. This review discusses updated genotyping and phenotyping methodologies, assay utilities and limitations, clinical validation studies, and current recommendations.