Best test for TB “Trojan Horse” found

A study co-authored by the University of Birmingham has discovered the most effective way to test people for latent tuberculosis (TB).

The results of a research partnership between the University, the Royal Centre for Defence Medicine, based at the Queen Elizabeth Hospital in Birmingham, and the Liverpool School of Tropical Medicine will help to improve the UK’s ability to identify people entering the country who have been infected with the bacterium that causes TB.

The study’s authors say that the find offers a strategy for diagnosing this “silent infection”, which is notoriously difficult to detect.

TB is a potentially fatal infection that has increased in the UK in recent years. The TB bacterium can persist in the body like a “Trojan Horse”, only to emerge and reactivate months or even years later. Therefore identifying and treating individuals with latent TB can prevent the disease developing and then spreading to others.

The research study was carried out over several months in 2012, involved 166 Nepalese soldiers recruited to the Brigade of Gurkhas of the British Army, who were tested for latent TB using all the tests currently available. One of these, T-Spot, was discovered to be better than others at detecting latent TB when used alone. The study found that nearly 20 per cent had latent TB using the T-Spot test.

As a result, the test has been adopted by the Ministry of Defence (MoD) as a more efficient way to identify latent TB infections, and could be used in civilian populations.

TB is caused by the bacterium Mycobacterium tuberculosis, and is spread through the inhalation of tiny droplets from coughs or sneezes of an infected person.

Most people don’t develop the disease after acquiring the infection, however, around two billion people around the world carry the bacteria in their body and five to ten per cent go on to develop active TB. Diagnosis of latent infections is a key strategy to control TB in countries like the UK.

Study co-author Professor Adam Cunningham said: “It has a wider importance because the way the study was performed allowed a more accurate assessment than has been possible previously.”