UK’s Cambridge-based Rapid Biosensor Systems (RBS) has developed a new screening test for early stage tuberculosis infection that is low cost, non-invasive and can be used in remote locations, since it does not require electricity or running water. The TB Breathalyser detects infected subjects capable of transmitting TB to others, giving a result in minutes with up 95% to accuracy.
The device, the result of six-year research and development program, consists of a collection tube, at the bottom of which is a glass bio-sensor coated with a patented bio-chemical coating that reacts with the TB bacilli. After the patient coughs into the tube, it is sealed with a simple twist action, and then inserted into a portable reader unit.
The reader contains a laser that scans the sample. The bio-chemical coating includes analogs coated with fluorescent material.
In what is known as a Displacement Assay process, the tuberculosis antigen displaces fluorescently-coated analogues and bonds more strongly to antibodies, creating a lessening of the fluorescent signal. The laser sees a signal change, and the unit calculates this as a positive test result. Elapsed time: 2 minutes.
“The most prevalent method of screening currently is the Mantoux TB test, which involves a health worker injecting test fluid under the patient’s skin, then waiting for up to 72 hours to see if there is a localised reaction that indicates the presence of TB. There are however, many factors that can influence the reaction, meaning that expert assessment – and with it a degree of subjectivity – is involved in interpreting the results. Further, the test is prone to delivering false positives or false negatives, implying that further testing and interpretation may be required,” says Dennis Camilleri, CEO of RBS.
Trials and Testing
So far, the Breathalyser has been validated in a series of clinical trials with over 500 patients in a hospital in India and in independent trials in Ethiopia, supervised by the London School of Hygiene and Tropical Medicine. A further trial at a WHO-approved hospital in South Africa is also nearing completion.
The Breathalyser is to be launched first in India and South Africa, ranked first and fifth respectively on the WHO list of high TB countries. The need for better screening is critical, with TB is at near-pandemic levels in both countries. Concurrent with the launch, RBS will begin the approvals processes via both the FDA and the MHRA that will be required to allow use of the Breathalyser in Europe and the USA.
“Although we have effective drugs against tuberculosis, it remains one of the world’s most serious public heath problems and kills more adults than any other single infectious agent. We urgently need ways of detecting infectious pulmonary cases early in the infection before the disease has a chance to spread”, notes Dr Ruth McNerney, senior lecturer at the London School of Hygiene and Tropical Medicine.
“The RBS Breathalyser test is unique”, she adds, “in that it does not require the collection of sputum samples, which are characteristic of advanced disease. That it does not need facilities such as electricity or running water and can be used outside of the hospital clinic means it could be used to screen people without them needing to visit the health centre. If the TB Breathalyser proves sufficiently sensitive then it might have a major impact on the way we control tuberculosis.”
Image by Carol Del Angel, Wellcome Images .
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