A5224s was a substudy of A5202 , a prospective trial of 1857 ART-naive participants randomized to blinded abacavir-lamivudine ( ABC/3TC ) or tenofovir DF-emtricitabine ( TDF/FTC ) with open-label efavirenz ( EFV ) or atazanavir-ritonavir ( ATV/r ) .