Prevalence of rifampicin resistance detected by Xpert was 3.3 % ( 95 % CI = 2.4 % , 4.3 % ) among new patients and 7.4 % ( 95 % CI = 4.3 % , 11.7 % ) among retreatment patients , with a 98 % ( 95 % CI = 87 % , 99 % ) positive predictive value compared to phenotypic drug susceptibility testing .