Discordant rifampicin susceptibility results are associated with Xpert® MTB/RIF probe B and probe binding delay

R. H. Berhanu, K. Schnippel, R. Kularatne, C. Firnhaber, K. R. Jacobson, C. R. Horsburgh, C. K. Lippincott

Research output: Contribution to journalArticlepeer-review

Abstract

S E T T ING: Xpertw MTB/RIF is the first-line diagnostic test for Mycobacterium tuberculosis and rifampicin (RIF) resistance in South Africa. OBJECTIVE : To describe the rates of Xpert RIF resistance not confirmed on follow-up testing, as well as the patient and test characteristics associated with discordant results. DESIGN: Retrospective review of patients with isolates showing Xpert RIF resistance. Line-probe assay, phenotypic drug susceptibility testing or repeat Xpert were all considered confirmatory tests of RIF resistance. 'Discordance' was defined as a patient with RIF resistance identified on initial Xpert testing, with a subsequent confirmatory test indicating RIF susceptibility. Associations were analysed using Pearson v2 difference of proportions and modified Poisson regression. RESULTS : RIF discordance occurred in 22/263 subjects and was associated with Xpert probe B, probe binding delay, as opposed to probe dropout, and probe binding delays (DCt) of between 4 and 4.9. CONCLUSION: Discordant RIF resistance was common in our cohort and was associated with Xpert probe delay and use of probe B.

Original languageEnglish (US)
Pages (from-to)358-362
Number of pages5
JournalInternational Journal of Tuberculosis and Lung Disease
Volume23
Issue number3
DOIs
StatePublished - 2019

Keywords

  • Discordance
  • Drug-resistant TB
  • Rifampicin resistance
  • TB

ASJC Scopus subject areas

  • Pulmonary and Respiratory Medicine
  • Infectious Diseases

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