Tongue swab testing on two automated tuberculosis diagnostic platforms, Cepheid Xpert® MTB/RIF Ultra and Molbio Truenat® MTB Ultima

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Abstract

Tongue dorsum swabbing is a potential alternative to sputum collection for tuberculosis (TB) testing. Previous studies showed that Cepheid Xpert® MTB/RIF Ultra (Xpert Ultra) can detect Mycobacterium tuberculosis (MTB) DNA in tongue swabs stored in buffer, with 72% sensitivity and 100% specificity relative to a sputum microbiological reference standard (sputum MRS). The present study evaluated a more convenient sample collection protocol (dry swab storage), combined with streamlined sample processing protocols, for side-by-side analysis using two commercial TB diagnostic tests: Xpert Ultra and Molbio Truenat® MTB Ultima (MTB Ultima). Copan FLOQSwabs were self-collected, or collected by study workers, from 321 participants in Western Cape, South Africa. All participants had symptoms suggestive of TB, and 245 of them had sputum MRS-confirmed TB (by sputum culture and/or Xpert Ultra). One tongue swab per participant was tested on Xpert Ultra and another tongue swab was tested with MTB Ultima. Xpert Ultra was 75.4% sensitive and 100% specific, and MTB Ultima was 71.6% sensitive and 96.9% specific, relative to sputum MRS. When sample lysates that were false-negative by MTB Ultima were frozen, thawed, and re-tested, MTB Ultima sensitivity rose to 79.1%. Both tests were more sensitive with swabs from participants with higher sputum Xpert semi-quantitative results. The protocol for Xpert Ultra enabled fast and easy testing of dry-stored swabs with no loss of accuracy relative to previous methods. MTB Ultima testing of dry-stored swabs exhibited comparable performance to Xpert Ultra. These results further support tongue swabs as easy-to-collect samples for high-throughput TB testing.

Article activity feed

  1. Lucian Davis

    Review 4: "Tongue Swab Testing on Two Automated Tuberculosis Diagnostic Platforms, Cepheid Xpert® MTB/RIF Ultra and Molbio Truenat® MTB Ultima"

    The reviewers found the methods rigorous, and with conclusions and interpretations supported by their results. Reviewers did comment that additional detail in describing their methods, such as by following established guidelines, would offer additional clarity.

  2. Soumitesh Chakravorty

    Review 3: "Tongue Swab Testing on Two Automated Tuberculosis Diagnostic Platforms, Cepheid Xpert® MTB/RIF Ultra and Molbio Truenat® MTB Ultima"

    The reviewers found the methods rigorous, and with conclusions and interpretations supported by their results. Reviewers did comment that additional detail in describing their methods, such as by following established guidelines, would offer additional clarity.

  3. Seda Yerlikaya

    Review 2: "Tongue Swab Testing on Two Automated Tuberculosis Diagnostic Platforms, Cepheid Xpert® MTB/RIF Ultra and Molbio Truenat® MTB Ultima"

    The reviewers found the methods rigorous, and with conclusions and interpretations supported by their results. Reviewers did comment that additional detail in describing their methods, such as by following established guidelines, would offer additional clarity.

  4. Rumina Hasan

    Review 1: "Tongue Swab Testing on Two Automated Tuberculosis Diagnostic Platforms, Cepheid Xpert® MTB/RIF Ultra and Molbio Truenat® MTB Ultima"

    The reviewers found the methods rigorous, and with conclusions and interpretations supported by their results. Reviewers did comment that additional detail in describing their methods, such as by following established guidelines, would offer additional clarity.

  5. Strength of evidence

    Reviewers: R Hasan (Aga Khan University) | 📗📗📗📗◻️
    S Yerlikaya (Heidelberg University) | 📗📗📗📗◻️
    S Chakravorty (Rutgers University) | 📒📒📒◻️◻️
    L Davis (Yale University) | 📗📗📗📗◻️