Performance of an Xpert-based diagnostic algorithm for the rapid detection of drug-resistant tuberculosis among high-risk populations in a low-incidence setting

PLoS One. 2018 Jul 16;13(7):e0200755. doi: 10.1371/journal.pone.0200755. eCollection 2018.

Abstract

Timely diagnosis of drug-resistant tuberculosis (DR-TB) is beneficial for case treatment and management. We implemented an algorithm to improve molecular diagnostic utilization to intensify DR-TB case findings. The GeneXpert MTB/RIF (Xpert) test was used for initial diagnosis. Samples with Mycobacterium tuberculosis complex (MTBC)-positive and rifampicin resistance (RR) results were subsequently and simultaneously tested using the GenoType MTBDRplus (DRplus) and MTBDRsl (DRsl) tests. This prospective cohort study enrolled 2957 high-risk DR-TB cases. We tested sputum specimens using conventional mycobacteriological and molecular tests. Gene sequencing was performed to resolve discordant results. According to the Xpert test, 33.6% of specimens were MTBC-positive and 5.1% were RR. RR specimens were further analyzed in the DRplus and DRsl tests. We identified 1 extensively drug-resistant (XDR), 8 pre-XDR, 18 simple multidrug-resistant (MDR), 22 mono-RR, and 2 RR cases with concurrent second-line injection DR-TB. Of these, 25 (49%) were relapses, 13 (25.5%) were treatment failures, 10 (19.6%) were from MDR-TB high-incidence areas/countries, 1 was from MDR-TB contact and 2 were unknown. Among culture-positive TB cases, the sensitivities, specificities, and positive predictive values (PPVs) of the Xpert test and RR cases were 73.6% and 100.0%, 85.7% and 98.6%, and 73.5% and 80.0%, respectively. Gene sequencing of discordant results revealed 7 disputed rpoB mutations and 2 silent mutations for RIF, 1 ahpC mutation for isoniazid and 1 gyrA mutation for fluoroquinolone. The algorithm effectively identified approximately 23% of annual MDR-/XDR-TB and 37.5% of RR-TB cases that were enrolled in our DR-TB treatment and management program within 3 days.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Algorithms
  • Antitubercular Agents / pharmacology*
  • Communicable Disease Control
  • Drug Resistance, Bacterial*
  • Female
  • Fluoroquinolones / pharmacology
  • Genotype
  • Humans
  • Incidence
  • Isoniazid / pharmacology
  • Male
  • Microbial Sensitivity Tests
  • Middle Aged
  • Mutation
  • Mycobacterium tuberculosis / drug effects
  • Mycobacterium tuberculosis / genetics
  • Predictive Value of Tests
  • Prospective Studies
  • Rifampin / pharmacology*
  • Sequence Analysis, DNA
  • Taiwan
  • Tuberculosis, Multidrug-Resistant / drug therapy*
  • Tuberculosis, Multidrug-Resistant / epidemiology
  • Tuberculosis, Multidrug-Resistant / microbiology
  • Tuberculosis, Pulmonary / diagnosis

Substances

  • Antitubercular Agents
  • Fluoroquinolones
  • Isoniazid
  • Rifampin

Grants and funding

This research was supported by grants from Taiwan CDC, Ministry of Health and Welfare (Grant number: MOHW105-CDC-C-315-123104 and MOHW106-CDC-C-315-113701 to RJ). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.