We examined plasma specimens obtained during a randomized , double-blinded trial in antiretroviral therapy ( ART ) - naive HIV-infected adults which compared the efficacy of elvitegravir/cobicistat/emtricitabine / tenofovir disoproxil fumarate ( EVG/c/FTC / TDF ) with that of efavirenz/emtricitabine/tenofovir disoproxil fumarate ( EFV/FTC/TDF ) .