Photo Credit: University College London

A new blood test that could predict the onset of tuberculosis (TB) three to six months before people become sick has been discovered by researchers at University College London. Published in The Lancet Respiratory Medicine, the researchers identified gene expression signatures present in the blood of people with early, asymptomatic TB infection that could predict the disease before symptoms arise. This new test could help save countless lives and help develop new target antibiotics.

Tuberculosis is a contagious infection caused by a bacterium that mainly affects the lungs, as well as other organs. In 2017 alone, TB caused 10 million incident cases and 1.6 million deaths, accounting for more deaths than other infectious disease worldwide. Early infection causes no symptoms and remains inactive, which makes it hard to diagnose before complications arise.

To begin the study, the researchers reviewed all published work on gene signatures present in the blood of people with TB and identified 17 gene expressions.

A total of 1,100 blood samples in published data sets from the UK, South Africa, Ethiopia and The Gambia were analysed. This blood was given from people who had no TB symptoms at the time, and were then followed up to see which participants went on to develop TB after a few months.

Eight of the 17 signatures were found to be predictive of TB in the early stages. They could be diagnosed three to six months before symptoms develop, falling into the accuracy required by the World Health Organisation (WHO) for new diagnostic tests.

Lead author Dr. Rishi Gupta (UCL Institute for Global Health) said: “The emergence of gene expression signature tests, which can aid diagnosis and early treatment, provides real hope for the management of infectious diseases. In this study we identify multiple signatures to identify the onset of tuberculosis, which is extremely encouraging, potentially providing multiple targets for early detection.

“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—a disease which causes the greatest number of deaths worldwide due to any single infection. The availability of multiple signatures will help to broaden access to these tests.”

Corresponding author, Professor Mahdad Noursadeghi (UCL Infection & Immunity), said: “About one-quarter of the world’s population is thought to have been infected with the bacteria that cause TB. The majority of these individuals remain well and cannot transmit the disease.”

“However, we currently do not know which people are most likely to develop TB disease after being infected. If we can identify these individuals, we can treat their infection more easily and prevent it from spreading to others.

“Our findings establish the gene signatures in blood which show most promise for identifying people who are at risk of disease. 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.”