New Tool Enables Easier Diagnosis of TB in Children

Around 240,000 children worldwide die of tuberculosis every year. The disease is among the top ten causes of death in children under the age of five. One of the main reasons for this mortality is that tuberculosis is often misdiagnosed or not diagnosed in time, particularly in regions with limited resources. A new diagnostic tool, which an international research consortium led by LMU medical scientists Laura Olbrich and Norbert Heinrich from the Division of Infectious Diseases and Tropical Medicine at LMU University Hospital Munich has tested as part of a large-scale study in five countries, offers significant progress in this area. The authors report on their findings in The Lancet Infectious Diseases.

Before now, the most commonly used tuberculosis tests have been based on microbiological analysis of sputum – that is, mucus taken from the lower airways. These samples are difficult to obtain in children. Moreover, child tuberculosis is often characterized by a low bacterial load and unspecific symptoms. “Therefore, new tests are urgently needed,” says Olbrich.

Simple, rapid blood test

The new tool, which the researchers have now tested, is based on the activity of three specific genes, which can be measured in capillary blood. An innovative, semi-automatic system allows health care workers to identify a so-called transcriptomic signature for these genes. This transcriptomic signature can help to diagnose tuberculosis. The test has the advantage that the blood sample can be conveniently taken from the fingertip and the results are available very quickly: “We have the results in just over an hour. For most other tests, the samples have to be sent to other laboratories for analysis,” says Olbrich.

“The results were encouraging,” says 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.” As the reference signature of the new tool was largely identified from adult samples, the researchers expect that the test accuracy can be further improved after adjusting the calculation of the signature for children.

Reference: Olbrich L, Verghese VP, Franckling-Smith Z, et al. Diagnostic accuracy of a three-gene Mycobacterium tuberculosis host response cartridge using fingerstick blood for childhood tuberculosis: a multicentre prospective study in low-income and middle-income countries. Lancet Infect Dis. 2023. doi: 10.1016/S1473-3099(23)00491-7

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