Diagnostic reliability of Xpert MTB/RIF with rifampicin resistance detected at very low bacterial level: a retrospective analysis

doi:10.19871/j.cnki.xfcrbzz.2021.04.012

Abstract

Abstract: Objective To evaluate the reliability of Xpert MTB/RIF assay with rifampicin resistance detected at very low bacterial level on sputum and bronchoalveolar lavage fluid specimens and provide reference for tuberculosis diagnosis. Methods A total of 4476 respiratory specimens detected by Xpert MTB/RIF assay were reviewed. Among them, 95 specimens yielded test results of “MTB detected, very low; Rifampicin resistance detected”. A retrospective analysis of these 95 results was performed to compared the consistency of rifampicin resistance detected by Xpert MTB/RIF and culture-based DST and repeated Xpert MTB/RIF. And the treatment outcome of 9 patients with discordant results was analyzed. Results There were 93 respiratory specimens sent for liquid culture and 65 reported MTB positive and 28 MTB negative. In the 59 culture-based DST, 51 showed rifampicin resistant and 8 rifampicin susceptible. The consistency of Xpert and DST was 86%（51/59）; 28 specimens were sent for a repeated Xpert and 20 turned out MTB positive, of which 16 were found to be rifampicin resistant at the same probe as the first Xpert. 4 showed no rifampicin resistance detection. The consistency of two Xpert tests were 80%（16/20）; 9 patients with discrepant results were successfully cured, 8 with first line medicine and 1 with second line regimen. Conclusion Xpert MTB/RIF shows reliability in detecting rifampicin resistance even ata very low bacterial load, but a repeated Xpert or culture-based DST is recommended for more precise diagnosis.

Key words: Mycobacterium tuberculosis, Rifampicin resistance, Low bacteria load, Treatment outcome

Chen Tao, Wang Yuxiang, Zheng Junfeng, Li Tianpin, Ye Feidi, Ye Taosheng, Deng Guofang, Zhang Peize. Diagnostic reliability of Xpert MTB/RIF with rifampicin resistance detected at very low bacterial level: a retrospective analysis[J]. Electronic Journal of Emerging Infectious Diseases, 2021, 6(4): 319-322.

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