Tongue swab-based Targeted Universal Tuberculosis Testing in people living with HIV in KwaZulu-Natal, South Africa

In many parts of the world, finding tuberculosis early is a matter of life and death, yet the standard way to test for it creates a barrier for the very people who need it most. The disease is typically diagnosed by asking a patient to cough up a sample of mucus from deep in their lungs, a process known as sputum collection. For someone who is already feeling unwell or who is struggling with a weakened immune system, producing this sample can be difficult, painful, or simply impossible. When a patient cannot provide the sample, the test cannot happen, and the infection remains hidden. This gap is particularly dangerous for people living with HIV, whose immune systems are compromised and who are at a much higher risk of developing active tuberculosis. Researchers have long sought a way to test these individuals without relying on a deep cough, looking for a method that is gentle, easy to perform, and capable of catching the disease even when the patient has no obvious symptoms.

A team of scientists in KwaZulu-Natal, South Africa, decided to explore whether a simple swab of the tongue could replace the difficult task of collecting lung mucus. They focused on a strategy called Targeted Universal Tuberculosis Testing, which means checking everyone in a high-risk group for the disease, regardless of whether they feel sick or are actively looking for medical care. The goal was to see if a non-invasive tool could find the bacteria in people who might otherwise slip through the cracks. The researchers gathered a group of 251 people living with HIV, most of whom were visiting local clinics to start treatment for their HIV infection. The group was diverse, with a median age of 34, and included more women than men. While two-thirds of the participants reported having symptoms that could be related to tuberculosis, the study was designed to test everyone, ensuring that those without symptoms were not overlooked.

To conduct the experiment, the medical staff collected samples from each participant using two different types of swabs. One type was a standard cotton-like swab, and the other was a foam swab. Alongside these tongue samples, the team also collected urine and, when possible, the traditional lung mucus samples to serve as a reference point. The tongue swabs were then processed using advanced molecular techniques designed to detect the genetic material of the tuberculosis bacteria. The researchers compared the results from the tongue swabs against the results from the urine and the lung mucus to see how well the new method performed. They found that the tongue swab method was highly specific, meaning it did not falsely flag healthy people as sick. However, when it came to finding the disease, the swabs detected about half of the cases that were confirmed by the more traditional methods.

The study revealed that the tongue swab approach was more effective at finding tuberculosis than the urine test, which is another non-invasive method often used for people with HIV. This difference was especially clear among participants with very low immune system counts, a group that is most vulnerable to the disease. The researchers noted that the tongue swab method worked well even when the participants were not actively seeking care for tuberculosis symptoms. While the method did not catch every single case, finding roughly half of the infections suggests it is a powerful tool for screening large groups of people who might otherwise go undiagnosed. The results indicate that for people living with HIV, a simple swab of the mouth could be a practical and effective way to expand testing programs, reaching those who cannot or will not provide a sample from their lungs.

This work does not claim to have solved the problem of tuberculosis detection, nor does it suggest that tongue swabs are perfect. The study showed that the method missed nearly half of the cases, meaning it cannot replace all other forms of testing on its own. Instead, the findings suggest that tongue swabs offer a valuable addition to the toolkit, particularly in settings where collecting lung mucus is not practical. By identifying a significant portion of infected individuals who would otherwise remain undetected, this approach could help public health programs reach more people and treat the disease earlier. The research highlights a path forward where simple, non-invasive methods are combined with sensitive laboratory techniques to protect the most vulnerable members of society.