Prevalence and significance of HIV-1 drug resistance mutations among patients on antiretroviral therapy with detectable low-level viremia.

HIV-1 resistance testing was performed in 47 antiretroviral (ARV)-treated subjects with low-level viremia (LLV) of <1,000 copies/ml. The median viral load was 267 copies/ml. In those with ≥2 LLV episodes, 44% accumulated additional resistance mutations. Fewer active ARVs and longer elapsed time were associated with an increased risk of resistance accumulation after controlling for adherence and viral load. Virologic failure followed 16% of LLV time points. Strategies for early intervention after LLV episodes should be further studied.