Published in PLOS One on 2025-10-27, this study is presented as an attributed evidence briefing. The excerpts below are the original researchers’ words, reproduced under their Creative Commons Attribution licence. Health Signal has selected the abstract and, where needed, opening background paragraphs; the complete methods, results, limitations and references remain in the linked paper.
Original study title: Challenges, innovations and considerations for the use of tongue swabs in Mycobacterium tuberculosis complex detection
Original authors: Anura David, Keneilwe Peloakgosi-Shikwambani, Zanele Nsingwane, Violet Molepo, Wendy Stevens, Lesley Scott
Source: PLOS One • DOI 10.1371/journal.pone.0325585
Read the complete primary study ↗ · Creative Commons Attribution licence
From the researchers
Abstract
Sputum-based testing is most used for diagnosing pulmonary tuberculosis (TB), but non-sputum specimens such as tongue swabs (TS) offer additional approaches for detecting Mycobacterium tuberculosis complex (MTBC). This two-phase study evaluated various storage, transport, and processing conditions to improve MTBC detection using TS tested on quantitative PCR (qPCR) and Xpert MTB/RIF Ultra (Ultra).
Adults (≥18 years) with Ultra-positive sputum were enrolled at a healthcare facility in Johannesburg, South Africa. In Phase 1, five serial TS were collected per participant and transported “dry” at 2–8°C, to the testing laboratory. In Phase 2, seven TS were collected: three stored “dry,” two in Tris-EDTA (TE) buffer, and two in PrimeStore® Molecular Transport Medium (MTM). Across both phases, pre-testing methods included heat lysis (HL)-only or HL combined with vortex bead beating (VBB), and storage at varying temperatures before qPCR. Swabs stored in MTM were tested on Ultra.
A paired t-test revealed no statistically significant differences in Ct values between sequentially collected TS (adjusted p > 0.05). Similarly, mean IS6110/IS1081 Ct values did not differ between fresh and frozen samples (t (85) = −0.031, p = 0.98; 95% CI: –0.44 to 0.43). VBB significantly reduced Ct values compared to HL alone (t (85) = −9.67, p = 2.422 x 10-15; 95% CI: −2.44 to −1.61). While storage conditions influenced Ct value and consistency to some extent, mean Ct values varied slightly from 32.48–34.28. Ultra detection improved when TS were processed with MTM and SR buffer.
MTBC detection from serially collected TS was variable, but Ct values were consistent across swab order and storage conditions. VBB improved yield on qPCR, and Ultra detection was enhanced with diluted SR buffer, highlighting the value of optimized processing. These findings support the continued development of TS-based TB diagnostics.
Introduction
The diagnosis of tuberculosis (TB) typically relies on sputum and other respiratory specimens for bacteriological confirmation [1]. However, additional specimen types such as urine [2], stool [3] and more recently tongue swabs (TS) [4] have shown value in detecting Mycobacterium tuberculosis complex (MTBC). Tongue swabs offer a non-invasive option for populations where sputum collection is difficult, such as children, people living with HIV (PLHIV), or individuals with paucibacillary disease [4]. Multiple studies have demonstrated the feasibility of detecting MTB DNA from tongue dorsum samples using molecular methods such as Xpert® MTB/RIF Ultra (Ultra) (Cepheid, Sunnyvale, CA, USA) [5,6]. Compared to sputum, TS are easier to collect, require minimal training and are acceptable to patients [7]. Swabs also have an added advantage in that they can be self-collected [7]. While sensitivity tends to be lower than that of sputum, especially in individuals with low bacterial loads [7] ongoing research is focused on improving sensitivity and facilitating implementation in resource-limited settings.
Reading this evidence
Use the full paper to check the study design, participant selection, comparator and outcome definitions before drawing a practical conclusion. An association does not by itself show cause and effect. A reported performance measure needs its denominator and uncertainty. A finding from a particular facility, sample or time period should retain that scope when it is discussed elsewhere.
This briefing makes the source accessible within the wider technology & industry desk. It does not assess an individual patient or certify a product. When considering relevance to another health system, examine the original authors’ account of context and limitations, then seek local implementation evidence. The related reporting below provides other studies to read alongside this one; it is a topic connection, rather than a claim that their results are directly comparable.
© 2025 Anura David, Keneilwe Peloakgosi-Shikwambani, Zanele Nsingwane, Violet Molepo, Wendy Stevens, Lesley Scott. Excerpts reproduced under CC BY. Selection, formatting and contextual notes by Health Signal. The researchers are the authors of the source study, not members of Health Signal’s staff.
Explore connected evidence
- Evidence brief: Diagnostic accuracy of the TrueNat™ MTB plus assay for detecting pulmonary tuberculosis in adults
- Evidence brief: Mycobacterium tuberculosis complex lineages and drug resistance patterns among tuberculosis patients with or without diabetes mellitus in southern Ghana
- Evidence brief: Annual trends in Mycobacterium tuberculosis detection and rifampicin resistance at a regional referral hospital in Northern Ghana, 2019–2024
