Novel approach identifies people at risk of developing TB: Lancet study

NEW DELHI: A novel approach to studying the progression of tuberculosis (TB) from infection to disease can identify and treat people at increased risk of developing the disease that current methods of testing would not, according to a study published in The Lancet Microbe journal.

Researchers at the National Institute for Health and Care Research (NIHR) Leicester Biomedical Research Centre (BRC), UK, hope the findings could help with global efforts to reduce the spread of the disease. TB is a bacterial disease that causes significant lung damage and can, without treatment, be fatal. It is spread in aerosol by inhaling droplets containing the bacteria.

Most people who become infected live with the infection and remain well. However, in a small proportion, the infection is not controlled and can progress to cause disease.

“Current tests of TB infection use either a skin test or a blood test, called an interferon gamma release assay (IGRA) to detect an immune response to the infection. However, these tests cannot distinguish between those that are at high or low risk of developing TB,” said Pranabashis Haldar from the University of Leicester and a Principal Investigator at the NIHR Leicester BRC, where the research was carried out.

“An important research goal is to develop better tests that can identify the high-risk group so that we can provide more targeted treatment to prevent TB developing,” Haldar said. The latest study used PET-CT, a highly sensitive form of imaging, as a novel way of looking at how the infection progresses, and to identify people at greater risk of developing the disease.

This approach allowed the team to undertake a study evaluating a potential new blood test for identifying those at higher risk, without needing to recruit a large cohort, which can be challenging and very expensive.

“In PET-CT scans, patients are given fluorodeoxyglucose (FDG), a radiotracer which is similar to naturally occurring glucose (a type of sugar) that the body uses it in a similar way,” Jee Whang Kim, a Clinical Research Fellow from the University of Leicester, who conducted the study said.

“By analysing the areas where the radiotracer is taken up, it’s possible to identify areas in the body where something might be going on,” Kim added.

The researchers found that the radiotracer activity tended to be taken up around the lungs, or in lymph nodes around the lungs. In this study, the team used a novel bacteriophage-based assay called Actiphage. The Actiphage assay uses a bacteriophage that attacks live TB bacteria; releasing the bacterial DNA which can then be detected.

Using this approach, it is possible to detect very low levels of bacterial DNA that cannot otherwise be detected using existing clinical tools.