Low-Abundance Drug-Resistant HIV-1 Variants: Finding Significance in an Era of Abundant Diagnostic and Therapeutic Options

(See the article by Simen et al., on pages 693–701.) Several prospective and retrospective studies have shown that genotypic testing for drug-resistant HIV-1 variants has helped health-care providers better un-derstand patient responses to antiretrovi-ral therapy (ART) andmakewiser choices for both initial and salvage therapy. The standard approach to genotypic resis-tance testing begins with plasma HIV-1 RNA extraction, reverse transcription, and polymerase chain reaction (PCR) amplification, and it ends with the direct sequencing of PCR products by use of the standard dideoxynucleotide terminato