For the proportions of patients ( intention-to-treat ; missing = failure ) with HIV-1 RNA < 400 copies/mL ( PI group , 66 % ; ABC/3TC/ZDV group , 71 % ) and < 50 copies/mL ( PI group , 63 % ; ABC/3TC/ZDV group , 62 % ) at 96 weeks , switching to ABC/3TC/ZDV was noninferior compared with continuing the PI regimen ; the difference in failure rate ( ABC/3TC/ZDV minus PI ) was -4.4 percentage points [ 95 % confidence interval ( CI ) -21.0 to +12.3 percentage points ] and +0.4 percentage points ( 95 % CI -16.9 to +17.7 percentage points ) , respectively .