Tongue swabs match sputum for TB diagnosis in four countries

Diagnosing tuberculosis (TB) usually depends on examining sputum, the mucus people cough up, but producing a usable sputum sample can be hard for many patients—in particular children and people living with HIV. Tongue swabs, a simple swab taken from the surface of the tongue, are a promising alternative because they are easy to collect and almost everyone can provide one. To test whether tongue swabs could deliver similar real-world results to standard sputum-based testing, researchers led by Caitlin A. Moe screened consecutive people with symptoms of TB at health centers in the Philippines, Vietnam, Uganda, and Zambia between September 2024 and January 2025. They enrolled 1,639 people seeking TB testing and asked each person to provide a tongue swab and to follow routine referral for sputum collection. The study focused on diagnostic yield—the number of positive molecular test results among everyone seeking testing—because a test that is slightly less sensitive but much easier to collect might find as many cases overall. The study was conducted in routine clinical settings to reflect how these tests perform in real life.

The study compared tongue swab testing using the MiniDock MTB Test (Guangzhou Pluslife Biotech Co., Ltd., China) in research laboratories to sputum testing done with WHO-recommended molecular testing per national guidelines. Of 1,639 participants, 851 (51.9%) were female, 415 (25.3%) were living with HIV, and 132 (8.1%) were children under age 5. Nearly every participant gave a tongue swab (1,637 of 1,639; 99.9%), while 1,389 (84.7%) provided sputum. Diagnostic yield was similar: tongue swab testing identified 63 positive results out of 1,639 people (3.8%), and sputum-based molecular testing identified 68 positive results out of 1,639 people (4.1%). The difference in yield was -0.3% with a 95% confidence interval of -1.2 to +0.6, which fell within the pre-specified non-inferiority margin of ±3%. Results were consistent across countries, ages, sexes, and HIV status. The work was supported by the Bill and Melinda Gates Foundation.

These findings show that, in routine care, tongue swabs can produce a diagnostic yield for TB that is non-inferior to sputum-based molecular testing. Because almost everyone could give a tongue swab—especially groups who struggle with sputum production, like young children and people living with HIV—swab-based approaches may detect as many cases in practice as sputum testing even if the test itself is slightly less sensitive. The study used a low-cost molecular platform and suggests that swab-based testing could be scaled up as an alternative where collecting sputum is difficult or where smear microscopy remains the primary diagnostic method. The authors call for further operational research to integrate tongue swab testing into existing diagnostic algorithms and to explore deployment in diverse health systems. Overall, these results support broader use of tongue swabs to simplify and expand access to TB diagnosis.