In this multicenter , randomized , double-blind , placebo-controlled trial , we assigned previously untreated patients with HCV genotype @ infection , in a @:@ ratio , to an active regimen consisting of a single-tablet coformulation of ABT-@ / r-ombitasvir ( at a once-daily dose of @ mg of ABT-@ , @ mg of ritonavir , and @ mg of ombitasvir ) , and dasabuvir ( @ mg twice daily ) with ribavirin ( in doses determined according to body weight ) ( group A ) or matching placebos ( group B ) .