Application evaluation of GeneXpert MTB/RIF assay in the detection of rifampicin resistance and multidrug resistant tuberculosis / 国际检验医学杂志

ABSTRACT

Objective To explore the application values of GeneXpert MTB/RIF assay (Xpert assay) for rifampicin resistance and multidrug resistant tuberculosis (MDR-TB).Discordance of Xpert and L-J proportion DST of rifampicin was analyzed.Methods Specimens of 1 300patients from January 2014to June 2016in our hospital were collected for solid culture, Xpert assay and L-J proportion drug susceptibility test (DST).Rifampicin resistance detected by Xpert assay was compared with L-J proportion method as a gold standard.Sequencing of rpoB gene and determination of minimum inhibition concentration were accomplished on the discordant MTB strains between Xpert and L-J proportion DST.Results Compared with the DST, the sensitivity, specificity, positive and negative predictive value of Xpert assay for rifampicin resistance were 99.31％, 97.82％, 92.88％and 99.80％, respectively.Among 1 300culture-positive specimens, mutations were detected from 309specimens by Xpert assay, which included 125initial treatment and 184retreatment patients.Among309specimens with rpoB gene mutations, mutations detected by probes E, D and B were common, and the rates were 65.70％, 14.56％and 10.68％, respectively.Totally 239patients were MDR-TB[77.35％ (239/309) ], of which 94initial treatment patients[75.20％ (94/125) ]and 145retreatment patients[78.80％ (145/184) ]were MDR-TB.Among 22strains which were detected rpoB gene mutations by Xpert, but sensitive by L-J proportion DST, 6strains had no mutation in rpoB gene rifampicin resistance determining region (RRDR);16strains had mutations, which were mainly located in L511Pcodon (8strains) and L533Pcodon (4strains).Among 2strains which had no rpoB gene mutation by Xpert, but were resistant by L-J proportion DST, 1strain had no mutation in rpoB gene RRDR region;1strain had mutation which was located in E546G codon outside RRDR region.Conclusion Xpert assay can be used to rapidly detect rifampicin resistance and to screen MDR-TB.Mutations in codon 511and 533are related to low-level resistance to rifampicin.