From the Departments of *Pediatrics and †Laboratory Medicine, University of Washington, Seattle, WA.
Received for publication September 30, 2003; accepted December 13, 2003.
Reprints: Dr Lisa M. Frenkel, 4800 Sand Point Way, NE, 8G-1, Seattle, WA 98105 (e-mail: firstname.lastname@example.org).
Abstract: Infection with drug-resistant HIV-1 may result from the acquisition of mutant strains or from their selection within the individual; either can compromise the efficacy of antiretroviral therapy (ART). Drug-resistance testing is recommended to assist in the choice of ART. Herein, factors that contribute to the selection of drug-resistant virus and details important to the interpretation of the genotypic and phenotypic susceptibility test results are reviewed.