Of the 1931 patients who underwent randomization , in the per-protocol analysis , a favorable outcome was reported in fewer patients in the isoniazid group ( 85 % ) and the ethambutol group ( 80 % ) than in the control group ( 92 % ) , for a difference favoring the control group of 6.1 percentage points ( 97.5 % confidence interval [ CI ] , 1.7 to 10.5 ) versus the isoniazid group and 11.4 percentage points ( 97.5 % CI , 6.7 to 16.1 ) versus the ethambutol group .