Published: 03 August 2023
Researchers from St George’s, University of London have worked with a medical technology company to create and test a new diagnostic device which could help to diagnose the millions of undiagnosed tuberculosis (TB) cases worldwide each year.
Three million undiagnosed TB cases every year
Around 10 million people are infected with TB every year, and 1.4 million die. The WHO estimates that there are approximately three million undiagnosed cases per year, largely in under-resourced areas where TB is endemic. These cases contribute significantly to the spread of the disease.
TB is traditionally diagnosed by analysing sputum samples under a microscope to detect the Mycobacterium tuberculosis (Mtb) bacteria. Though not an expensive or complex technique, it cannot detect low-level infections, and requires specialist training. Culturing samples is much more sensitive but takes longer and requires biosafety facilities which may not be available in resource-limited settings.
Accurate and sensitive diagnostic tests which are rapid, cheap, and portable are crucial to reducing TB cases, as well as addressing drug resistance.
The study by Moore, CM et al, published in July in the Journal of Molecular Diagnostics, was the result of a partnership between researchers in the Institute for Infection and Immunity at St George’s and the medical technology company QuantuMDx Ltd, which St George’s has had longstanding collaborations with in the areas of TB and malaria research.
'Lab-on-a-chip' technology
The new device, currently at prototype stage, employs ‘lab-on-a-chip’ technology called CAPTURE-XT® which uses microfluidics to process sputum samples and capture any Mtb bacilli it contains for visual analysis by microscopy (to replace smear microscopy). This purified sample can also be used to confirm infection by quantitative PCR, as well as for drug-susceptibility analysis.
The technology uses dielectrophoresis, a technique which selectively attracts or repels specific particles or cells based upon their properties in a particular type of electric field. The Mtb bacteria are specifically captured and concentrated, while the other sputum contents are washed away. Enriching the samples in this way means that even low levels of bacteria can be detected.
The test was fine-tuned using a set of 50 known sputum samples and then tested using a further set of 100 known sputum samples stored by the Foundation for Innovative New Diagnostics (FIND).
Overall, it accurately detected samples as negative 100% of the time and detected positive samples 87% of the time, with this increasing to 100% for samples with a higher amount of bacteria present.
Increased accessibility could boost diagnoses
Together the results point to the device being the basis of a point-of-care diagnostic test, with the potential addition of being able to identify the bacteria for screening programmes or with genotyping for drug susceptibility testing.
The partnership model used to develop the device has potential to benefit global health more broadly.
“This new chip-based technology could bring diagnostics to the people that need it and also, by more accessible case-finding, prevent the further spread of this disease. Collaboration between university-based academic researchers and biotechnology industry scientists presents a way forward to develop new approaches for some of the world’s greatest healthcare challenges, such as TB.”
- Professor Philip Butcher, Professor of Molecular Medical Microbiology in the St George’s Institute for Infection and Immunity -
Learn more about the research at the Institute of Infection and Immunity