Ryan K. Shields, PharmD, MS: T2Candida's Place in Rational Antifungal Management

Segment Description: Ryan K. Shields, PharmD, MS, associate professor of medicine at the University of Pittsburgh and Contagion®'s Multidrug-Resistant Infections Section Editor, discusses his research presented at MAD-ID 2019 on T2Candida's place in rational antifungal management.

Interview transcript (modified slightly for readability):

Ryan K. Shields, PharmD, MS: This year at MAD-ID 2019 I presented research on behalf of a larger team about our ways we’ve incorporated T2Candida into diagnostic management in our medical ICU. T2Candida is a new diagnostic test that’s really important because it detects candida directly from whole blood samples within 3 to 5 hours. Comparatively, it takes 2 to 3 days to diagnose candidemia in blood cultures, which we know delays antifungal therapy for patients. So we view T2 as a way to find patients with candidiasis where we can initiate earlier antifungals and we hope to be able to improve their outcomes with that.

The other thing that’s tricky about T2 and all these new diagnostic tests is defining the right patient population that needs to be tested. We started with a pilot study in our medical ICU where we looked at patients in septic shock who were on vasopressors for at least 3 hours and we asked teams to order both blood cultures and T2Candida in parallel so we could compare the results of T2Candida to the blood culture. Now, the test was only approved by our stewardship team, which is also an important way where we restricted the test through diagnostic stewardship to make sure we could test only the right patients.

After the test was collected and sent to the microbiology lab, the results were also called back to our stewardship team so we could facilitate antifungal therapy and educate teams on what the test means for their patients. In doing so, we were able to find patients that were positive by T2Candida and initiate antifungal therapy much sooner. In fact, all of the patients in our study that had a T2Candida-positive result received antifungal therapy within 8 hours of blood cultures being collected. Comparatively, [for] patients that did not have a T2-positive result and were only diagnosed by blood cultures alone, it took 3 or sometimes 4 days for those patients to be started on antifungals. Positive test is one of the most important applications of T2Candida because it helps you initiate antifungal therapy much sooner.

We’ve been able to use the negative predictive value of the test to withhold or discontinue antifungal therapy in patients that are started. This is really important to us in our medical ICU because we’ve been able to control and guide antifungal usage with both positive and negative tests. After our pilot period, we found that we were able to decrease antifungal usage overall by 47% and, in fact, we decreased our median duration days of therapy from 26 days of antifungals down to 15 by using T2.

We concluded from the study that T2Candida was very useful in our patient populations to both start antifungals sooner and also to stop or withhold antifungals in high-risk patients because of the predictive value of the test. We also found that using T2Candida in conjunction with blood cultures, we were to diagnose more patients with candidiasis than would be diagnosed with blood culture alone. That’s because we feel like T2 might detect the bug earlier in the disease process where blood culture are generally much later in the disease process and it takes time for them to turn positive. T2 in conjunction, at our institution, with diagnostic stewardship has been a successful approach and has led us now to expand what we’re doing with T2 into other patient populations. This includes our surgical and trauma ICUs for patients that might have intra-abdominal surgery and be at-risk for deep-seated candidiasis, as well as our cardio-thoracic ICU where we’ll be looking at patients on long-term mechanical circulatory support, which would include patients on LVAD, or who have ECMO support, and maybe these patients are also at high-risk for candidiasis and we can use T2 to use antifungals appropriately for them.

The study, “Incorporating T2Candida Testing into Rational Antifungal Management: A Successful Pilot Study of Diagnostic Stewardship Directed Toward Specific Intensive Care Unit Patients At-risk for Sepsis Due to Invasive Candidiasis,” was presented at the 22nd annual Making a Difference in Infectious Diseases (MAD-ID 2019) meeting.