A single swab is all it takes: Study paves the way for easier tuberculosis detection
An international research team led by scientists from Heidelberg University’s Faculty of Medicine and the University of California, San Francisco (USA), has investigated a new method for diagnosing pulmonary tuberculosis. This method enables tuberculosis bacteria to be detected quickly and easily via a simple swab, without the need for laboratories. The researchers applied the method to patients in seven countries with a high prevalence of tuberculosis and demonstrated that the test is diagnostically accurate and can be performed by untrained personnel. The results were recently published in the New England Journal of Medicine and played a key role in the World Health Organization’s recommendation for the global use of this diagnostic method.
This method enables the detection of tuberculosis bacteria (Mycobacterium tuberculosis) using a tongue swab at the point of sample collection in under 35 minutes. Two portable devices are used for diagnosis: in one, the bacteria in the swab sample are lysed for further analysis. The second device evaluates the sample by detecting genetic material and uses indicator lights to show whether the sample is “positive” (containing bacterial genetic material) or “negative” (not containing bacterial genetic material). The reliability of the results obtained using this method, and whether the individual steps can be safely performed by untrained personnel, were investigated by Claudia Denkinger, Professor of Infectious and Tropical Medicine at Heidelberg University’s Faculty of Medicine, Medical Director of the Department of Infectious and Tropical Medicine at Heidelberg University Hospital (UKHD) and Dr. Seda Yerlikaya, Group Leader in Infectious and Tropical Medicine, together with international research partners. Prof. Denkinger and Dr. Yerlikaya are both scientists in the German Center for Infection Research (DZIF).
Study design and key findings
The study, which was recently published in the New England Journal of Medicine, tested 1,380 individuals with suspected pulmonary tuberculosis using the new method at outpatient centers in India, Nigeria, South Africa, Uganda, Vietnam, Zambia, and the Philippines. The patients provided sputum samples (secretions coughed up from the respiratory tract) and tongue swabs. For both sample types, the researchers determined the proportion of patients correctly identified as infected (sensitivity) and the proportion of healthy individuals correctly identified (specificity). The results showed that the tuberculosis test using tongue swabs correctly identified four out of five infected individuals (80 percent sensitivity) and produced false positives in only 0.5 percent of those tested (99.5 percent specificity). The diagnostic accuracy of the new method when applied to sputum samples was comparable to that of laboratory-based molecular diagnostics, which are currently considered the reference standard for tuberculosis detection. In a parallel study, the researchers demonstrated that the new tongue swab test can identify as many TB cases as previous sputum-based TB diagnostic methods despite the lower sensitivity.
“We have demonstrated that the method meets the World Health Organization’s standards for tuberculosis diagnostics,” summarizes lead author Dr. Yerlikaya. “The results are so compelling that the WHO has already recommended its use for adolescents and adults with symptoms typical of TB.” The research team also confirmed the test’s user-friendliness.
According to Prof. Denkinger, the fact that a tongue swab is sufficient for diagnosis not only simplifies sample collection, but also expands the pool of test subjects. This is because not all patients suspected of having tuberculosis can provide a sputum sample. This applies, for example, to children, severely ill individuals, and HIV-positive people, who are at increased risk of TB infection. The infectious disease specialist cites further advantages: “The devices are compact in size, can be operated by laypeople without extensive training, provide clear results quickly, and are battery-powered.” The latter is crucial for use in regions where a continuous power supply is not guaranteed. In addition, the costs for the near-point-of-care test are significantly lower than those for laboratory tests.
Development of the method, WHO recommendations, and outlook
Prof. Denkinger and her team were already involved in the development of the new methodology—contributing technical expertise and conducting supporting studies, among other things. The project received financial support from the National Institute of Allergy and Infectious Diseases (NIAID) of the U.S. National Institutes of Health (NIH), the Gates Foundation, the U.S. Department of State (formerly USAID), and the European Union as part of the European and Developing Countries Clinical Trials Partnership (EDCTP).
Now that the World Health Organization (WHO) has recommended the procedure as the first “near-point-of-care test” for tuberculosis, preparations are currently underway for its pilot implementation in various countries with high TB burdens. Several organizations and foundations are funding the initiative, including the Global Fund to Fight AIDS, Tuberculosis and Malaria and the Children’s Investment Fund Foundation. “For the diagnostic procedure to be successfully implemented internationally, it’s not just a matter of procuring the necessary equipment and materials. Implementation also requires defining target populations and testing sites, training users, engaging stakeholders and adapting deployment strategies to country-specific contexts,” says Prof. Denkinger, outlining the next steps. Crucial to the success of the new diagnostic tool is that both medical professionals and the people being tested gain confidence in the new testing procedures.
Background: Tuberculosis—an infectious disease and its diagnosis
More than one million people worldwide die from tuberculosis (TB) every year. In 2024 alone, there were over ten million new cases. TB is a bacterial infectious disease that primarily affects the lungs, but it can also affect other organs. Symptoms include a persistent cough, fever, and weight loss. While tuberculosis can be treated with antibiotics, diagnosis poses a challenge. Existing tests are expensive, time-consuming, and sometimes inaccurate. Furthermore, in countries with high infection rates and limited resources, access to these tests is limited. Often, there is a shortage of trained personnel, necessary laboratory equipment, and a reliable power supply for laboratory devices. Diagnosis typically does not take place at the point of care, i.e., where patients present themselves. As a result, results are delayed, and necessary treatment cannot begin immediately. Some patients are never reached at all. “Against this backdrop, TB detection via tongue swab is setting new standards in TB diagnostics,” says Prof. Denkinger.
Further information:
“Factsheet Tuberculosis” of the World Health Organization
Source:
Press release of Heidelberg University Hospital (in German)
