(Reuters) - Two immune system molecules could form the basis of a new
test to quickly detect whether tuberculosis is dormant or active and infectious,
U.S. researchers said on Sunday.
"A rapid test that could tell the difference between latent and active
tuberculosis would be a major step forward," said Dr. Jason Stout of Duke
University Medical Center who presented his findings at the American Thoracic
Society meeting in New Orleans.
Doctors could more quickly treat active infections, helping to limit the spread
of the disease, Stout said.
Current blood tests can distinguish between people who are infected with TB and
those who are not but they cannot tell whether an infection is active or
dormant. It takes a culture test that grows the TB bacilli to show if it is
active or not, and that can take weeks.
Stout and colleagues collected blood samples from 71 people with active TB,
latent TB or no infection at all.
They added a bit of TB bacteria to the blood samples to stimulate an immune
response, then measured the activity of 25 immune signaling chemicals called
cytokines to try to identify a pattern that could be used as a signature of
active TB infection.
"We found that a pattern of two cytokines, called MCP-1 and IL-15, was
reasonably good at differentiating between persons sick with TB and persons
infected but not sick," Stout said.
A third cytokine called IP-10 also showed promise at sorting between people who
are infected and those who are not.
Stout said other studies have pointed to these three cytokines individually as
possible TB markers, but his is the first to put all three together as a
possible TB test.
"These findings could lead to earlier diagnosis of active tuberculosis, which
could be beneficial for both the sick person and others around her or him who
might be spared from infection," Stout said in a statement.
Tuberculosis killed 1.8 million people in 2008, or nearly 5,000 people a day. It
is caused by the Mycobacterium tuberculosis bacteria. More than 2 billion
people, or about a third of the world's population, are thought to be infected.
It is not only a scourge in poor countries but also in the West, where it has
flared anew in the last 20 years because of AIDS, which weakens the immune
system.
TB can be cured with antibiotics, but they need to be taken daily for months to
be effective. Because people often skip doses, multiple drug resistant forms are
spreading and the World Health Organization says the hard-to-treat infection is
spreading.
Source : Reuters
