Detection of tenofovir in plasma samples , compared with no detection and as measured in seroconverters and a subset of non-seroconverters , was associated with an 85 % relative risk reduction in HIV-1 acquisition for the tenofovir disoproxil fumarate group ( HR 015 , 95 % CI 006-037 ; p < 00001 ) and 93 % for the emtricitabine plus tenofovir disoproxil fumarate group ( 007 , 002-023 ; p < 00001 ) .