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New research has used a novel ‘glow in the dark’ approach to study ‘leaky gut’, a key feature of a condition known as environmental enteropathy (EE) in which a damaged gut allows harmful matter to enter the bloodstream.

EE is a major contributor to undernutrition, a global health problem that accounts for nearly half of all deaths in children under the age of five, and limits physical and mental development in millions more. 

In this , research participants in Zambia and the UK drank a harmless, fluorescent liquid (fluorescein) and had a painless light sensor attached to their finger.

In all participants, the liquid leaked through the gut into their blood stream and was detected by the fingertip sensor. This is possible as fluorescein emits visible light (fluorescence) when illuminated with blue or ultraviolet light. Higher fluorescent signals were observed in the Zambian group, indicating greater leakage of fluorescein through the gut wall into the blood stream.

No need for samples

The low-cost, non-invasive technique – known as transcutaneous fluorescence spectroscopy (TFS) – trialled in this study has the potential to offer a cheaper, quicker and non-invasive alternative to EE testing, which could be a game changer in low-income settings. Beyond EE, it may also have important implications for other gut disorders like coeliac disease, irritable bowel syndrome and inflammatory bowel disease.

No need for clinical labs

The current method of EE testing requires a biological sample (urine, stool or blood), which needs to be tested in a clinical laboratory. This is costly, not readily available in all low-income countries, and takes longer (often weeks or months) to return results than the TFS approach, where reporting of results within 3-4 hours of testing is feasible. 

Small, portable, affordable

The TFS approach, on the other hand, only requires a small, portable finger sensor and a small dose of fluorescein. It is user friendly, and doesn’t require clinical or technical expertise, suggesting it could potentially be deployed at home or in a community setting in the future. 

Next steps

Having conducted the pilot research on 51 participants (34 in Zambia and 17 in the UK), the researchers have already embarked on larger studies in both the UK and Zambia to test the approach and technology on a larger scale. This includes studies in healthy volunteers in the UK, healthy adults from higher socioeconomic groups in Zambia, and children undergoing treatment for undernutrition, also in Zambia.

They are also looking at ways to make the finger sensor smaller, lighter and wearable, so it can send the results wirelessly for analysis.  

The research was led by the Hamlyn Centre and other 911½ñÈÕºÚÁÏ colleagues, Queen Mary University of London and the University of Zambia, and formed part of an international collaboration that also included the University of Glasgow and the University of Zimbabwe.

These results provide a proof-of-concept showing that we can measure changes in the gut barrier using TFS, with a method that is much less intrusive and hopefully also more reliable than existing tests. While there is still work to do to further improve and optimise the technology, we are hopeful that this can be useful in providing advanced monitoring and better study of a wide range of gut disorders in the future. Dr Alex Thompson Hamlyn Centre, one of the lead authors

Professor Paul Kelly from Queen Mary and the University of Zambia, the other lead author, added:

“This is potentially very exciting as a quick, non-invasive test that would be useful to diagnose multiple digestive diseases, not only in Africa, but also in intensive care settings. 

“It could help in clinical care, but also in research on ways of reducing the leaky gut. This is an important step forward.”

The paper, "", is out now in the new BMJ journal .

This work was funded by the UK (MRC) through the (Novel tools for evaluating intestinal dysfunction in children and adults with malnutrition disorders).

Infrastructure support was provided by the .