A 22-year-old woman with HIV presents for follow-up and monitoring on an antiretroviral regimen of rilpivirine-tenofovir DF-emtricitabine. Baseline laboratory studies performed prior to starting antiretroviral therapy showed the CD4 count was 323 cells/mm³, HIV RNA level was 43,250 copies/mL, and there were no mutations on an HIV drug-resistance genotypic assay. She initially achieved an undetectable HIV RNA level, but recently, after some problems with adherence, had two HIV RNA levels greater than 500 copies/mL.