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Breath Test for TB Developed!

The search for a quick and simple tuberculosis test has taken a tremendous step forward as scientists in the US develop the world’s first breath test for the disease.

Tuberculosis, or TB as it is otherwise known, affects around 8.6 million people in the world each year, and killing 1.3 million, which makes it second only to HIV.

According to the World Health Organisation (WHO), the best defense against TB is early diagnosis and treatment, but that is not an easy feat. The current method involves multiple drugs administered over a period of six months.

It is failure to complete this course of treatment that has led to a rise in MDR-TB – multidrug-resistant tuberculosis. In some countries, this strain of the infection alone accounts for 30% of its TB cases.

Diagnosis of TB used to rely on waiting for a month to six weeks while the bacteria was cultivated. This was done in the patient’s sputum, which is a combination of mucus and saliva coughed up from the patient’s respiratory tract.

A WHO-approved DNA detection technique called GeneXpert has been used in the last few years, to detect whether a sample of sputum has TB bacteria in it and whether the strain is resistant to one of the key drugs. This only take three hours, but it still doesn’t give full drug-resistance information, and there is still a long wait involved.

“Optimally treating somebody the best you can at the time of that single encounter, so someone can go home with the right set of tablets, would be really, really useful,” declared lead researcher Dr Graham Timmins.

Building on their previous TB work, Dr Timmins and his colleagues at the University of New Mexico based their latest research on an inhaled form of antibiotic called isoniazid. This inhalant is commonly used to fight the infection and is activated by the TB enzyme.

Dr Timmins said the team realised they could actually see the conversion of isoniazid to its activated form. They could do this by molecularly-labelling nitrogen, one of the gases that are given off when the antibiotic is activated by TB bacteria.

To test the inhalant, it was administered to some laboratory rabbits, and between five and 10 minutes later, breath samples were taken. These samples were put into a special machine called a mass spectrometer to be chemically analysed. A positive result, showing labelled nitrogen emissions in the sample, indicates that TB bacteria is present and that these bacteria are likely to be treatable with isoniazid. The work has been published in Nature Communications.

Of course, the breath test is still in the early stages and currently only detects sensitivity to the antibiotic, so it would need to be used in conjunction with other tests. But the next step it to put the method to clinical trials.

Even if the breath test is only shown to work in humans when used alongside other tests, it will still speed up the diagnostic process. The quicker tuberculosis is diagnosed, the sooner it can be treated, and the more lives that can be saved.


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