Resistance in Early Antiretroviral Treatment Failure?

Virologic rebound early in treatment is frequently associated with genotypic resistance, but the source of resistant viruses has not been fully elucidated. One possibility is that preexisting low-frequency resistance mutations emerge during treatment failure. To evaluate this possibility, investigators studied 4 patients who experienced early virologic failure on an initial treatment regimen (tenofovir, 3TC, and an NNRTI — either efavirenz or nevirapine) and 18 control patients who received comparable treatment but did not experience virologic failure.

None of the patients had demonstrable resistance mutations on population-based genotypic sequencing conducted before treatment initiation. However, use of an allele-specific real-time PCR assa…