As compared with the rate of sustained virologic response in the group that received 8 weeks of ledipasvir-sofosbuvir , the rate in the 12-week group was 1 percentage point higher ( 97.5 % CI , -4 to 6 ) and the rate in the group that received 8 weeks of ledipasvir-sofosbuvir with ribavirin was 1 percentage point lower ( 95 % CI , -6 to 4 ) ; these results indicated noninferiority of the 8-week ledipasvir-sofosbuvir regimen , on the basis of a noninferiority margin of 12 percentage points .