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T2 Biosystems Candida Sepsis Test Proves Value in Clinical Study


NEW YORK (GenomeWeb) – A molecular diagnostic test for blood-borne fungal infections from T2 Biosystems has the potential to dramatically raise the standard of care in clinical practice. The T2Candida Panel provides twice the accuracy in a tiny fraction of the time it takes to currently diagnose sepsis caused by Candida species, a new study published this week in Clinical Infectious Disease said.

Simply put, T2Candida is better at diagnosing sepsis due to Candida than blood culture is, in just about every way. And the benefits extend to patients, reducing mortality, as well as health care providers, reducing costs.

A $1.5 million clinical trial study, funded by T2 and led by Eleftherios Mylonakis of Brown University's Alpert Medical School, evaluated the $250 T2Candida Panel and $150,000 T2Dx platform. The test, which was approved by the US Food and Drug Administration in September, can detect the five most common species of Candida that cause sepsis, using the firm's T2MR magnetic resonance technology to detect a PCR-amplified signal. The fully automated platform takes whole blood samples and can display results on screen or integrate them into electronic medical records. The technology is sensitive enough to find 1 colony forming unit per mL of blood.

"It's a paradigm shift of what we need now as the standard, which is to get away from culture. Blood culture is really very poor," Mylonakis said. "Up until this point it has been the standard of care but it misses half of the cases of Candida in the blood."

Testing mostly patient samples spiked with the different Candida species at levels common to infected patients, along with actual patient samples of patients at risk for infection, the T2Candida Panel was able to detect the pathogens in 91.1 percent of cases, with overall specificity of 99.4 percent. Perhaps most importantly, the test slashed the time it takes to diagnose Candida infection from five days down to less than five hours. The study found that T2Candida took an average of 4.4 hours to get a positive result, compared to 129 hours for blood culture and species identification, and an average of 4.2 hours to return a negative result, compared to at least 120 hours.

That is particularly important for Candida infection because clinicians are working with a very small window of opportunity to correctly treat the patient. "Candida bloodstream infection has mortality above 30 percent," Mylonakis said. "What makes prompt diagnosis more important is that mortality can decrease by half or more if you get the patient drugs in the first 12 hours. If you wait for the cultures, you have a mortality that goes up every day that you wait."

Getting patients treated quickly and correctly also means they can get out of the hospital sooner.  According to T2 CEO John McDonough, the average patient spends approximately 40 days in the hospital with an average of nine days in the intensive care unit at a cost of approximately $130,000 per patient. "If you can get the patient on the right drug in 24 hours, for the patients who survive, it reduces the length of hospital stay by nine days," McDonough said. That could be worth $30,000 in savings for hospitals, which usually get reimbursed a fixed amount for the patient. For a high-volume hospital that tests as many as 5,000 immunocompromised patients per year, the savings could be worth millions, McDonough said.

Determining which patients don't need anti-fungal therapy is also important. Because of the small window of opportunity to treat Candida infection, patients often receive unnecessary anti-fungal drugs, which can lead to drug-resistance and have toxic side effects, Mylonakis said.

For those cases where Candida is present, the test provides actionable information on which anti-fungal drugs to use, since there is a solid body of research showing that different species of Candida are best treated with different anti-fungal drugs.  

T2Candida can also correctly diagnose infection in cases where blood culture fails. "Sometimes we have invasive infection that isn't a persistent blood stream infection," Mylonakis said. He pointed to a case in the study where the test diagnosed an abdominal infection in a patient, when 12 separate attempts at blood culture failed to return a positive result.

McDonough said he expects to see a steady flow of smaller clinical studies T2 has funded coming out this year with results on the effectiveness of T2Candida and T2Dx. He said the firm has two other products in development, including T2Bacteria, a similar molecular diagnostic test for sepsis caused by bacteria. T2 is funding a study for that test which will start at the end of 2015, with results available in 2017 at the earliest.

The US Food and Drug Administration took an active role throughout the development and validation of T2Candida and T2Dx. The FDA reviewed the technologies through its de novo classification process for low- to moderate-risk devices that are the first of a kind. The products were cleared in less than four months, "a record for the FDA," McDonough said.

The FDA also helped with study design, Mylonakis said. Because blood culture performs so poorly, "not having a good comparator makes it difficult to demonstrate the benefits of the assay," he said. Infection was confirmed by both T2Candida and blood culture in only four of the patient samples. To help address this, the FDA recommended the use of a "contrived" arm of the study that featured 250 patient samples spiked with Candida species.

"The FDA gave useful feedback, which is an improvement from before," Mylonakis said. "This is a new approach but it signifies a bigger shift over the last few years to help new diagnostics come to market in a more efficient way."

McDonough said that T2 has just begun actively marketing its platform and test. At the JP Morgan Healthcare Conference held earlier this week in San Francisco, he also said that T2 expanded from three to seven sales representatives in 2014, and that the company hopes to close contracts during 2015 with 30 of what it has identified as the top 450 US hospitals for sepsis treatment.