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Assess the diagnostic performance of a revised tongue swab protocol for TB testing.

April 30, 2026The International Journal of Tuberculosis and Lung Disease1 citations

Tongue swab Xpert MTB/RIF Ultra testing for TB using a revised consensus protocol

Key Points

Assess the diagnostic performance of a revised tongue swab protocol for TB testing.
Participants aged ≥12 years with presumptive TB from clinics in four countries were enrolled.
Tongue swabs processed with Sample Reagent and phosphate buffer were tested with Xpert Ultra.
Sensitivity and specificity were compared to culture-based standards and sputum tests.
1,168 participants enrolled, with a median age of 37 years; 18.5% culture-confirmed TB.
Non-actionable results decreased to 5.6% overall, <4% in all countries except South Africa (15.4%).
Tongue swab sensitivity was 66.0%, specificity was 99.6%.

Abstract

BACKGROUNDTongue swabs are a promising specimen type for TB diagnosis. In a previous study, using a consensus protocol, tongue swabs tested with Xpert MTB/RIF Ultra outperformed sputum smear microscopy, but a substantial proportion (6.1%) of results were non-actionable (e.g., invalid/error). We evaluated a revised protocol for tongue swab Xpert Ultra testing in four high-burden countries.METHODSParticipants aged ≥12 years with presumptive TB were enrolled from outpatient clinics in the Philippines, South Africa, Nigeria, and Zambia. Tongue swabs were processed using Sample Reagent (SR, Cepheid, USA) diluted 2:1 with phosphate buffer or phosphate-buffered saline and tested with Xpert Ultra. Diagnostic performance was assessed against culture-based microbiological reference standard and compared to sputum tests.RESULTSFrom March to November 2024, 1,168 participants were enrolled (median age 37 IQR: 28-48 years; 46.7% female; 21.8% living with HIV; 18.5% culture-confirmed TB). The proportion of non-actionable tongue swab results was 5.6% overall, but CONCLUSIONThe revised protocol yielded low error rates at most sites and moderate sensitivity, supporting tongue swabs as an alternative specimen for Xpert Ultra testing when sputum is unavailable..

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