An international team of researchers has developed a fast, accurate and non-invasive method for diagnosing TB, an infectious disease that threatens the lives of over 10 million people every year. Created with support from the EU-funded A-Patch project, the new method uses a patch that absorbs TB-specific compounds that are detected in air trapped above the skin. Although TB is a treatable and curable disease, diagnosis remains a serious obstacle. At the moment, about 3 million active cases are missed by global health systems and the disease’s non-specific symptoms lead to millions of patients receiving incomplete or delayed diagnoses. Current diagnostic tests are also slow, not sensitive and/or specific enough, and too complex for places with limited resources. For example, mycobacterial cultures take 4 to 8 weeks, and at least 3 visits are needed before a patient’s diagnosis is finalised and treatment can begin. Another serious barrier is cost. A sputum smear costs EUR 2.2 to 8.9 per examination, which can be prohibitive considering that the overwhelming majority of TB cases occur in developing countries – in some of which people live on as little as EUR 1 a day. The need for a fast, cheap and sputum-free test for diagnosing TB led to the creation of this patch that is applied to the patient’s inner arm. The patch contains a pouch of absorbent material for capturing a variety of TB-specific volatile organic compounds (VOCs) that are released into the bloodstream by infected cells and can be detected in air trapped above the skin. When VOC values deviate from the healthy VOC range, this indicates either TB infection or a high risk of infection. The skin-based TB VOCs are detected and translated into a point-of-care diagnosis using a specially designed array of nanomaterial-based sensors.
Trialling the patch
The research team tested their absorbent skin patch in clinical trials in India and South Africa. The study population included newly diagnosed and confirmed active TB cases, healthy volunteers and confirmed non-TB cases. The patch proved to be highly effective in diagnosing the disease and met the World Health Organization’s criteria for a highly sensitive and specific new TB triage test that isn’t affected by difficult factors such as HIV status and smoking habits. The results have been published in the journal ‘Advanced Science’. “Our initial studies, done on a large number of subjects in India and in South Africa showed high effectiveness in diagnosing tuberculosis, with over 90 % sensitivity and over 70 % specificity,” observed study first author Dr Rotem Vishinkin of A-Patch project coordinator Technion – Israel Institute of Technology in a news item posted on the ‘Medical Dialogues’ website. “We showed that tuberculosis can be diagnosed through the compounds released by the skin. Our current challenge is minimizing the size of the sensor array and fitting it into the sticker patch.” The A-Patch (Autonomous Patch for Real-Time Detection of Infectious Disease) method promises to provide precise diagnoses of TB patients fast, easily and cost-effectively, without the need for specialised personnel. As important, the same method could in the future be used to also diagnose and monitor other diseases, such as COVID-19, in parts of the world that most need it. For more information, please see: A-Patch project website
A-Patch, tuberculosis, TB, skin patch, diagnostic tests