Rapid Fingertip Blood Test Accurately Diagnoses Tuberculosis in Children

A key issue contributing to these numbers is the frequent failure to diagnose the disease correctly or in a timely manner, especially in resource-limited settings. Traditional methods for diagnosing tuberculosis generally rely on microbiological analysis of sputum, or mucus collected from the lower airways. This is a challenge in children, who often have a low bacterial count in their sputum and show nonspecific symptoms. Now, a new diagnostic tool makes it easier to diagnose tuberculosis in children by requiring just a fingertip blood sample.

An international research consortium led by medical scientists at LMU University Hospital Munich (Munich, Germany) conducted extensive testing of this new diagnostic method in a large study spanning five countries. The tool operates on the basis of the activity of three specific genes measurable in capillary blood. Using an innovative semi-automatic system, healthcare providers can identify a transcriptomic signature for these genes, which aids in diagnosing tuberculosis. A significant advantage of this test is its convenience: the blood sample can be taken effortlessly from a fingertip, and the results are available in just over an hour. This is much faster than most other tests, which often require sending samples to specialized labs for analysis.

The new tool was evaluated during the RaPaed-TB tuberculosis study, conducted in collaboration with partners in South Africa, Mozambique, Tanzania, Malawi, and India. The study involved 975 children under the age of 15 who were suspected of having tuberculosis. To assess the test's accuracy, the children's tuberculosis status was also examined using a standardized reference test based on sputum analysis and bacterial cultures. Given that the reference signature for the new tool was mostly derived from adult samples, the researchers believe that the accuracy of the test can be enhanced further by fine-tuning the signature calculation for children.

“The results were encouraging,” said LMU medical scientist Laura Olbrich. “Compared to detection in culture, the test identified almost 60 percent of children with tuberculosis, with 90-percent specificity. This makes the test comparable with or better than all other tests that work with biomarkers. The bacterial culture is always the reference because it yields the most stable results. But it takes up to eight weeks and is often not available where children with tuberculosis present.”

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LMU University Hospital Munich