Lisa Isaacs

A GROUNDBREAKING new blood test can predict whether someone is likely to develop tuberculosis (TB) more than a year before the disease manifests itself.

Published today in leading medical journal The Lancet, and coinciding with World TB Day, a landmark study on the biomarker test has been hailed a game-changer in the fight against TB.

Doctors Without Borders says TB is now the leading infectious disease killer in South Africa, with 30 000 new cases diagnosed each year.

This 10-year discovery effort was led by scientists at the SA Tuberculosis Vaccine Initiative (SATVI) and the Centre for Infectious Disease Research (CIDR) in Seattle, US.

They studied gene expression patterns in blood samples of more than 6 000 teenagers from Worcester. The teenagers were observed for more than two years to identify those who did or did not develop TB.

Confirmation that the gene expression signature could predict TB was completed using samples from another group of 4 500 adults from South Africa and Gambia.

“The people we studied had evidence of infection of the TB bacterium already. In South Africa, approximately 80 percent of adults have evidence of infection with mycobacterium tuberculosis. But only a small proportion of these people will develop the TB disease.

“Our test, therefore, can differentiate between those who are infected and not at risk of progression to disease and those who are infected and likely to progress,” said the deputy director of immunology of SATVI, UCT Associate Professor Thomas Scriba.

“Targeting only those individuals who are truly at risk of tuberculosis disease for preventive antibiotic therapy is something that we desperately need in our battle against this devastating epidemic.”

This year, the blood test will be evaluated in a clinical trial, funded by the Bill & Melinda Gates Foundation, to determine if targeted preventive therapy for people with a positive test can stop them from developing TB.

A rapid, and simple to use, low-cost urine sample to test for TB at the bedside of HIV patients has been found to reduce the TB death rate of patients with advanced HIV by almost 20 percent. This is according to the findings of a multi-centre study led by principle investigator Professor Keertan Dheda of UCT.

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