The T2Candida Panel (T2 Biosystems) was the first diagnostic test for candidemia approved by the FDA. Using MRI to scan blood, it can detect the five most common species of Candida: C. albicans, C. glabrata, C. parapsilosis, C. tropicalis and C. krusei.
In the DIRECT2 trial, which was funded by T2 Biosystems, Cornelius J. Clancy, MD, associate professor of medicine in the division of infectious diseases and director of the mycology program at the University of Pittsburgh, and colleagues evaluated the panel in patients who had been diagnosed with candidemia via a blood culture.
“Invasive Candida infections are common causes of mortality and morbidity in hospitalized patients. Blood cultures are the current gold standard for diagnosing invasive candidiasis, but we know they’re negative for Candida in 50% or more of bloodstream-disseminated candidiasis,” Clancy told Infectious Disease News.
From March 2012 through August 2013, Clancy and colleagues enrolled 152 patients at 14 hospitals who had been diagnosed with one of the five Candida species and performed follow-up blood testing using the T2Candida panel and companion blood cultures. The median time between the collection of the original diagnostic blood cultures and the retesting of the samples was 55.5 hours. Most (74%) patients had been given at least one dose of an antifungal agent prior to obtaining the follow-up sample.
T2Candida had a sensitivity of 89%, obtaining positive results in 32 of 36 patients with positive companion cultures, Clancy and colleagues reported. They also found that the panel performed similarly to companion blood cultures in patients with recent candidemia who were not receiving antifungal treatment, with positive results in 32.5% of cases compared with 30%. In patients who were receiving treatment, the panel was positive in 50% of patients, and companion blood cultures were positive in 21% of patients.
“The data demonstrate that T2Candida reliably diagnosed candidemia when collected at a time that blood cultures were positive,” Clancy and colleagues wrote. “T2Candida may improve the management of candidemia by shortening times to Candida detection and species identification compared to blood cultures, thereby facilitating more rapid institution of definitive antifungal therapy.”
According to Clancy, nonculture tests like T2Candida have the potential to identify cases that are currently missed by blood cultures.
“Moreover,” he said, “the turn-around time for T2Candida is typically about 5 hours, compared to several days for blood cultures. Therefore, clinicians can get both positive or negative results more rapidly. The time to initiation of an active antifungal drug is a crucial determinant of survival in patients with candidemia.”
Clancy said the test was in development “many years” before the emergence of C. auris, but that there is “nothing from a technical standpoint” that would prevent it from being able to detect the invasive and often drug-resistant fungus that has been compared to a superbug. – by Gerard Gallagher
Reference:
Clancy CJ, et al. Clin Infect Dis. 2018;doi:10.1093/cid/cix1095.