Researchers have found that people who test positive with immunologic tuberculosis (TB) skin or blood tests rarely develop the disease.
It is because the infecting organism, Mycobacterium tuberculosis, is likely dead, wiped out naturally by people's immune systems, a new study suggests.
“The National Institutes of Health and other nonprofit organisations spend millions of dollars on studies of the latent state because of the assumption that TB infection is life-long, held in check by the immune system,” said study co-author Paul H. Edelstein from the University of Pennsylvania.
In their review, the team pointed to several previous studies to demonstrate the natural history of TB immunoreactivity in people given preventive treatment, and of active TB in immunoreactive people with various forms of severe immunosuppression, like patients with HIV and those who have received an organ transplant.
One study showed that the treatment of people with TB immunoreactivity for one year lowered the incidence of active TB by 60 to 70 per cent over the next nine years.
“TB immunoreactivity is not a marker for the presence of continued TB infection, rather, it serves as a sign of having been infected with TB at some point,” Edelstein said.
The study was published in the British Medical Journal.