A new test to rapidly and accurately diagnose TB infections

A research team has developed a new test which can quickly and accurately show whether someone is infected with TB and, for the first time, how serious the infection is.

The team, composed of scientists from Arizona, Washington DC and Texas, developed the test, named the NanoDisc-MS, after a recent World Health Organisation (WHO) consensus report deemed the development of rapid, effective ways to screen those infected by TB a ‘high priority’. The paper was published in the journal Proceedings of the National Academy of Sciences.

TB, a disease caused by the bacteria Mycobacterium tuberculosis, is a serious global health problem that can affect everyone but puts people in developing countries and those suffering from HIV infection at particular risk. The disease, which is usually based in the lungs but can spread to other parts of the body, can cause symptoms like fever and severe weight loss, and it’s been estimated by a WHO report in 2016 that TB infects 10 million people worldwide each year, causing 2 million annual deaths.

TB is a worldwide epidemic, with around 10 million people infected every year. Image credit: BBC.co.uk











One of the scariest things about TB is that it can exist in either an active state, in which the patient exhibits the symptoms, or a latent state, where the bacteria is ‘living’ inside the patient but hasn’t become infectious yet – before suddenly becoming active, at which point it becomes highly transmittable from person to person through the air by coughing or sneezing. The WHO estimate that around a third of the world’s population is infected with latent TB. No effective vaccine against the disease currently exists, and the number of drug-resistant strains is ever-increasing.

The MiniDisc-MS could represent one of the most significant developments in the diagnosis of TB infections of recent years. Whereas previous tests could take up to several weeks to come back with a result, the team’s new test only needs a few hours – a massively important factor to take into account, when treatment must begin as soon as possible to prevent the disease from spreading.

A faster diagnosis of TB infection could also significantly reduce the number of antibiotics which are wrongly prescribed, a major driving force behind the spread of drug-resistant bacteria.

In a press release Tony Hu, who led the team and is a researcher at Arizona State University Biodesign Institute, commented on the difficulties previous tests have faced. “In the current frontlines of TB testing, coughed-up sputum, blood culture tests, invasive lung and lymph biopsies, or spinal taps are the only way to diagnose TB. The results can give false negatives, and these tests are further constrained because they can take days to weeks to get results.”

The MiniDisc-MS test works by measuring the concentration of two key proteins in patient blood samples which are indicative of active TB infection, culture filtrate protein (CFP-10) and early secretory antigenic target (ESAT-6).

In tests, the test showed high sensitivity to detect CFP-10 and ESAT-6 in both lung-based TB and patients with TB in non-lung tissue (which is often harder to diagnose), with results of 91.3% and 92.3% sensitivity respectively.

HIV patients with TB were also diagnosed with a high degree of sensitivity. This is a noteworthy accomplishment, as HIV has been shown to interfere with the results of previous blood-based TB diagnostic tests, lowering their reliability.

The fact that the MiniDisc-MS is able to accurately measure the concentration of CFP-10 and ESAT-6 is important, because it would give physicians a clear idea of whether the anti-TB treatment they’ve prescribed is having an effect; a reduction in the concentration of these two proteins would indicate a successful treatment.

“We are particularly excited about the ability of our high-throughput assay to provide rapid quantitative results that can be used to monitor treatment effects, which will give physicians the ability to better treat worldwide TB infections,” Hu said. “Furthermore, our technology can be used with standard clinical instruments found in hospitals worldwide.”

Hu is currently developing the test further for clinical approval.

According to the paper, the relatively straightforward method by which they could detect disease-associated molecules means that the NanoDisc-MS could potentially be used to diagnose a wide range of other infectious diseases.

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