Tuesday January 28, 2020

Tuberculosis not a Life-long Infection in Most People, Says Study

The study was published in the British Medical Journal (BMJ)

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TB
A tuberculosis patient holds medicines at the Lal Bahadur Shastri Government Hospital at Ram Nagar in Varanasi, India, March 13, 2018. VOA

Researchers have found that people who test positive with immunologic tuberculosis (TB) skin or blood tests rarely develop the disease.

It is because the infecting organism, Mycobacterium tuberculosis, is likely dead, wiped out naturally by people’s immune systems, a new study suggests.

“The National Institutes of Health and other nonprofit organizations spend millions of dollars on studies of the latent state because of the assumption that TB infection is life-long, held in check by the immune system,” said study co-author Paul H. Edelstein from the University of Pennsylvania.

However, based on our analysis, we believe that it is rarely life-long, and in 90 per cent or more of infected people, there is no possibility of TB development even with severe immunosuppression,” Edelstein said.

In their review, the team pointed to several previous studies to demonstrate the natural history of TB immunoreactivity in people given preventive treatment, and of active TB in immunoreactive people with various forms of severe immunosuppression, like patients with HIV and those who have received an organ transplant.

One study showed that the treatment of people with TB immunoreactivity for one year lowered the incidence of active TB by 60 to 70 per cent over the next nine years.

Tuberculosis
FILE – A tuberculosis patient receives treatment at a clinic in Jakarta, Indonesia. VOA

Yet, those treated remained skin test positive for TB up to nine years later, showing TB immunoreactivity can outlast elimination of infection by at least nine years.

In another study, of patients co-infected with HIV and TB–who are at a higher risk for active TB–researchers showed that between 89 per cent and 97.5 per cent of those with positive TB immunoreactivity tests remained free of TB from their remote infection over a five-year period.

And in the third study of stem cell transplant patients, none of the 29 participants from the US cohort with TB immunoreactivity developed TB after a total of 89 person-years of observation.

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“TB immunoreactivity is not a marker for the presence of continued TB infection, rather, it serves as a sign of having been infected with TB at some point,” Edelstein said.

“We need to put more effort into controlling active TB and to determine how to detect the 10 per cent of people who actually do have a lifelong infection,” he added.

The study was published in the British Medical Journal (BMJ). (IANS)

Next Story

Gene Expression Signature in Blood May Predict Onset of Tuberculosis

This blood test may predict onset of tuberculosis

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Blood Test
Gene expression signatures in blood could be used to predict tuberculosis at a very early stage. PIxabay

Researchers, including one of Indian-origin, have revealed a blood test could predict the onset of tuberculosis three to six months before people become unwell, a finding which could help better target antibiotics and save countless lives. This test is a must for a healthy lifestyle.

For the findings, published in the journal Lancet Respiratory Medicine, researchers at University College London sought to identify which, if any, gene expression signatures in blood could be used to predict the disease at a very early stage and before symptoms

Gene expression signatures are single or combined measurements of levels of specific gene products and are being tested in a range of diseases to aid diagnosis, prognosis or prediction of the response to treatment.

Some are already being used to support the management of cancers, but none have reached the clinic in infectious diseases, such as tuberculosis (TB).

“Our findings establish the gene signatures in blood which show most promise for identifying people who are at risk of disease,” said study author Mahdad Noursadeghi, Professor at University College London.

Blood Test
The emergence of gene expression signature blood tests, which can aid diagnosis and early treatment, provides real hope for the management of infectious diseases. Pixabay

“Future development of a blood test based on these findings could make an important contribution to efforts to reduce the impact and spread of this deadly infection,” Noursadeghi added.

For this study, researchers initially conducted a systematic review of published gene signatures found to be present in blood samples from people with TB, compared to healthy individuals.

From this, 17 candidate gene expression signatures for TB were identified, and tested in more than 1,100 blood samples in published data sets from South Africa, Ethiopia, The Gambia, and the UK. Scientists analysed samples from people who had no TB symptoms at the time they gave blood. Those people were then followed up to identify which participants developed TB in the subsequent months.

Researchers found that eight of these signatures, including measurement of expression of a single gene, could predict the diagnosis of TB within three to six months, which falls within the accuracy required by the World Health Organisation (WHO) for new diagnostic tests.

This accuracy was achieved, by revealing the patients’ immune responses to bacteria before the symptoms of the disease develop. “The emergence of gene expression signature tests, which can aid diagnosis and early treatment, provides real hope for the management of infectious diseases,” said Indian-origin researcher and the study’s lead author Rishi Gupta.

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“In this study we identify multiple signatures to identify the onset of tuberculosis, which is extremely encouraging, potentially providing multiple targets for early detection,” Gupta added.

Further development of these tests could help identify people who will benefit most from preventative antibiotic treatment, in order to reduce the occurrence of tuberculosis, the researchers said. (IANS)