Researchers in the U.S. and the U.K. have developed a new radiotracer that promises an easier and more accurate way to detect tuberculosis (TB) — the world’s second leading infectious killer after COVID-19 — using PET scans.

The team, made up of researchers from the Rosalind Franklin Institute in the U.K., the Universities of Oxford and Pittsburgh and the U.S. National Institutes of Health, developed a radiotracer called FDT, which is taken up by live TB bacteria in the body. It uses a carbohydrate that is only processed by the TB bacteria and can be produced without specialist expertise or laboratories.

Current tests to diagnose TB either look for TB bacteria in a patient’s saliva and mucous or use a PET scan and the common radiotracer FDG to detect signs of inflammation in the patient's lungs. These tests can lead to patients being treated for either shorter or longer than necessary, as spit tests can provide negative results before the disease has been fully treated in the lungs and inflammation can remain after the TB bacteria is gone. Tests for inflammation can show the extent of the disease, but inflammation can be caused by other conditions, so the test isn’t accurate for detecting TB bacteria.
The new method only requires a hospital to have standard radiation control and PET scanners, and the new molecule is created from FDG using a relatively simple process involving enzymes developed by the research team.

Low- and middle-income countries currently see over 80% of TB cases and deaths around the world and the new testing method would be a viable option for these countries, according to the researchers.

Ben Davis, science director of the Franklin Institute’s Next Generation Chemistry group, who led the research, said FDG is the world’s most abundant source of the Fluorine-18 radioisotope.

“Production of FDG has been greatly enhanced globally by the guidance of the International Atomic Energy Agency, leading to the commercialization of ‘drop-in’ FDG production facilities by some companies, such as GE, that enables a given hospital or region to distribute to many hospitals, or to entire regions, such as the joint research center cyclotron in northern Italy,” Davis told HCB News. “This has been enhanced of late by the development of ‘mini’ cyclotrons allowing new production facilities at lower infrastructure.”

In the U.K., around 70 hospitals routinely use FDG, compared to around 100 in India, 500 in Japan and 600 in China, with the number continually growing in the latter three countries, Davis said.

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