New blood test speeds up diagnosis of blood infection
Testing for Candida in the bloodstream — a cause of sepsis with a 40 percent death rate — requires culturing blood in a laboratory to determine if the fungal yeast is present.
But that can take three days and even longer, with only a 50 percent detection rate.
So, with no time to waste, physicians typically bombard the patient with antibiotic, antifungal and even antiviral medications to kill anything and everything that may be causing the systemic infection, despite drug side effects, high costs, and risks of causing antibiotic resistance.
Now comes T2 Biosystems, a medical supply and equipment company in Lexington, Mass., that’s developed a breakthrough blood test — the T2Candida Panel — to diagnose a Candida-based blood infection (known as candidemia) within five hours.
The DIRECT2 study of the testing method, led by University of Pittsburgh researchers and published recently in the journal Clinical Infectious Diseases, has confirmed the speed and accuracy of the T2Candida Panel testing, with the U.S. Foodand Drug Administration having cleared the device for use.
That means physicians now can get earlier test results, administer antifungal treatments more quickly and reduce or avoid the multidrug scattershot approach. Studies have yet to prove that
faster, more accurate testing results in fewer deaths, better outcomes and less drug resistance, but all indications point in those directions.
“The test finds Candida, but it is not yet known whether earlier detection saves lives. But it’s intuitive that the earlier the better.” said Cornelius J. Clancy, lead author of the study and associate professor of medicine in the University of Pittsburgh’s Division of Infectious Diseases. He also directs Pitt’s mycology program.
Several species of Candida can cause sepsis, with 10 to 15 percent of all sepsis cases involving Candida. But the cause of infection often isn’t known unless the patient dies and an autopsy is performed, Dr. Clancy said.
With T2Candida, a small vial of the patient’s blood is placed into the desktop instrument, which performs the testing automatically. Nanoparticles injected into the blood sample attach to one of the five most common infectious Candida species, which the instrument tracks and measures through magnetic resonance. The results specify whether Candida is present and, if so, which species. That in turn allows the physician to use a specific antifungal medication to kill the infection.
Finding nothing means antifungal medications aren’t necessary. Either way, the test offers medical advantages. The same technology now could be applied to other disease, including infections and early detection of cancers, Dr. Clancy said.
“With an accurate diagnosis, we can start the patient on the correct medication for the type of infection he or she has, which will hopefully allow us to stop the infection before it spreads — but also keep us from giving the patient a drug that won’t work and potentially contributing to drug resistance,” Dr. Clancy said. “For candidemia, we know that the shorter the time to administering an active antifungal medication to the patient, the higher the survival rate.”
Candida is found on our skin and colonizes in our gastrointestinal systems, where it typically causes no harm and serves as a regular member of our intestinal flora, Dr. Clancy said. But Candida also has a sinister side in causing vaginal yeast infections and oral thrush.
When it crosses over the gastrointestinal barrier into the blood, systemic blood infections (sepsis) can occur, especially in elderly people and those with chronic conditions or immune-system deficiencies.
The DIRECT2 study tested the new testing method against blood-culture testing in 152 patients, with the study concluding that T2Candida represents “an important advance in the diagnosis of candidemia” while also ushering in a new era of “rapid molecular testing.”
Further studies are underway to confirm that T2Candida is cost-effective and can identify infections that blood cultures fail to detect, better predict patient outcomes and shorten the time in administering antifungal medications. Further research also will determine to what degree it performs as advertised in reducing inappropriate use of antifungal medications and limits drug resistance.
T2 Biosystems funded the research, assisted with the study design, and collected and compiled the data from participating universities and health centers. Study authors did all data and statistical analyses and independently wrote the study.
The recently published study “captures the speed and accuracy advantages of the T2Candida Panel over the current standard of care,” said John McDonough, T2 Biosystems CEO. “The number of hospitals utilizing the [T2] instrument is growing, based on the clinical impact and the economic benefits associated with getting patients on the right therapy faster because of our results.
“This data demonstrates to other hospitals how T2’s technology and experience can enhance hospital stewardship, reduce costs and, most importantly, improve patient outcomes,” he said.