New blood test may accurately detect tuberculosis

Tuberculosis (TB), that often dodges physicians, can now be precisely detected with a new blood test that can eliminate more than 50 percent of the procedure that goes into detecting the disease.

The new test using interferon-gamma release assays (IGRA) will detect pre-existing TB infection (or latent TB), that might not present itself for many years, or until the body becomes weakened by another source.

"It is fairly uncommon that latent TB will reactivate - only about a 10 percent chance. Having said that, given the crowding in corrections facilities, the mass exposure of inmates to TB could be disastrous," said Wendy Wobeser, an infectious diseases expert at Queen's University, Ontario.

The IGRA test is more effective in detecting whether a patient is TB positive or not.

On the contrary, the current tuberculosis skin test (TST) requires two visits to determine the results: one to perform the test and then another visit a couple of days later to read the results.

Moreover, depending on how much the patient is exposed to other mycobacteria, the current TB test can give many false positives.

Under the study, 96 inmates were tested positive for TB via the TST test. However, when the IGRA test was used, only 31 of them were confirmed as true latent TB infection.

"What I found surprising was just how much discordance there was between the TST and IGRA tests," added Ilan Schwartz, who was a medical resident at Queen's University when the research was started.

However, the IGRA tests cannot prove that latent TB infections will progress into active TB until the patient begins to show symptoms.

According to the World Health Organisation (WHO), in 2012, 8.6 million people suffered from TB and 1.3 million died from the disease worldwide.