An experimental test could help doctors catch a deadly type of fungal
infection in the blood within a few hours, rather than the few days it currently
takes, a new study suggests.
The test, which is not yet on the market, looks for Candida
infection in the blood. The fungus is best known for causing common vaginal
yeast infections, but when it gets into the bloodstream it can cause serious
infections of organs and tissue throughout the body.
Candida blood infections - known as candidemia - are very rare in
healthy people, but they are the fourth most common type of blood infection
among US hospital patients, according to the US Centers for Disease Control and
The infection is typically transmitted through contaminated catheters, and
seen in seriously ill patients - such as those in the intensive care unit, or
with weakened immune systems.
Symptoms of candidemia
The symptoms of candidemia are vague, and include fever and chills, so
doctors use blood cultures to diagnose it. That means putting a blood sample in
a special broth that feeds the yeast organism until it grows enough to be
But Candida "is a slow grower," and it takes a few days to get blood
culture results back, said Thomas Lowery of T2 Biosystems, the Lexington,
Mass.-based company developing the new test.
By that time, it may be too late for the patient. About 40% of people with
Candida blood infections die, and delayed diagnosis bears part of the
blame, Lowery and his colleagues write in the issue of the journal Science
Getting a precise diagnosis is vital, Lowery said, both to confirm that it's
Candida, and to pinpoint which type it is. "You need to know the
specific Candida so you can use the right anti-fungal drug," he
In the new study, Lowery's team found that the test they've developed can
reliably detect the five most common species of Candida within about
The researchers used blood samples from healthy people and "spiked" them with
Candida yeast. They then analysed the samples with the new test and
with standard blood cultures. The two tests were in agreement on "positives" 98%
of the time.
An expert not involved in the research said the test's sensitivity is "very,
"This is preliminary, but the technology looks extremely promising," said
Christine Ginocchio, chief of infectious disease diagnostics at North Shore-LIJ
Health System in Lake Success, NY.
What's particularly "exciting" is that the technology could potentially be
used to test for other pathogens that cause serious bloodstream infections,
according to Ginocchio, who is also a member of the Infectious Diseases Society
of America's Diagnostics Task Force.
Ideally, Ginocchio explained, when doctors suspect a patient has a
bloodstream infection, they would be able to take a blood sample, directly test
it, then have a result in a few hours. The problem right now is that a blood
sample would normally not contain enough of the culprit bug - be it a fungus or
bacterium - to detect.
Plus, Ginocchio noted, the blood contains a lot of other genetic material
that gets in the way of spotting that bit of foreign-invader DNA. That's why
blood cultures are done.
The new test, which is based on so-called magnetic resonance technology,
essentially removes the "noise" coming from other material in the blood sample,
allowing it to zero in on the pathogen.
There is still more work to be done. "Now you'd like to see this tested in a
larger, multicenter trial," Ginocchio said.
The process would also need to be automated, she noted, to be feasible for
smaller community hospitals. T2 Biosystems' Lowery said the researchers are
working on making the method "fully automated."
Exactly what it would all cost is not known. But both Ginocchio and Lowery
said that if the test gets more patients on the right drug quickly, the cost
would likely be worth it.
According to Lowery's team, research suggests that with Candida
infections, starting the right anti-fungal drug within 12 hours can cut the
death rate from 40% to 11%.
Learn more about Candida
blood infections from the US Centers for Disease Control and
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