HIV treatment guidelines from many parts of the world, including Canada, China, the European Union, the United Kingdom and the United States, recommend that results from drug resistance testing should guide treatment decisions when adjusting ART regimens in patients with virologic failure. Virologic failure is defined as viral loads persistently > 200 copies/mL 6 months after treatment initiation (or adjustment).
ART regimens can be adjusted as necessary without testing for drug resistance for patients who are virologically suppressed, defined as an HIV viral load below the lower limit of detection (< 20 or 50 copies/mL) after > 6 months of regular ART. Individuals with HIV who have no history of drug-resistance mutations or virologic failure can likely switch to any regimen that has been shown to be highly effective in patients naive to ART.
Optimal prevention of perinatal HIV transmission requires prompt initiation of ART in HIV-positive patients who are pregnant. Thus, ART initiation should not be delayed pending resistance testing results for patients who are pregnant. The ARV regimen can be changed as necessary once the results are received.
For patients experiencing virologic failure while receiving non–long-acting ART, drug resistance testing is recommended while the patient is still receiving their ARV drugs; when that is not feasible, testing should be conducted within 4 weeks after discontinuing therapy. If > 4 weeks have elapsed since the ARVs were discontinued, resistance testing may still provide useful information to guide therapy; however, it is important to recognise that previously selected resistance mutations can be missed owing to lack of drug-selective pressure at the time of testing.
Learn more about treatment-resistant HIV.
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Cite this: Michael Stuart Bronze, Enrico Brunetti. Fast Five Quiz: Treatment-Resistant HIV - Medscape - Aug 14, 2023.