653 - Comparison of Yeasts identification by Biofire, Culture and ePlex for Quality Assurance purpose

Background: At the University of Kentucky Medical center (UKMC), positive fungal blood cultures are concurrently run through the Biofire Blood Culture Identification (BCID) panel which detects 5 Candida species. The newer platform, the GenMarkDx ePlex BCID-FP (fungal panel) is designed to detect 16 fungal targets. Our study compares the performance of the Biofire BCID panel’s with culture as the gold standard method. We examine the percentage of agreement by both testing methods and predict the performance of the GenMarkDx ePlex BCID-FP panel based on culture results. We also look at the number of other yeasts not included in Biofire BCID panel that could be picked up by the GenMarkDx ePlex BCID-FP panel.  

Methods: Positive fungal blood cultures from July 1, 2018 to June 30, 2019 were run through the Biofire BCID panel. Culture results were used to extrapolate whether the GenMarkDx ePlex FP would provide any additional diagnostic benefit. Results were categorized as true or false positives and negatives as compared to culture as the gold standard.

Results: A total of 141 blood cultures were tested via the Biofire BCID panel for the identification of yeasts. Of these, 123 (87%) yielded Biofire results in concordance with culture results. We would expect these also to be positive on the GenMarkDx ePlex BCID-FP panel. In addition, 18 specimens (13%) would have tested positive on the GenMarkDx ePlex BCID-FP panel and not the Biofire BCID panel. These organisms were noted to be Candida lusitaniae (n=6), Cryptococcus neoformans (n=3), Candida dublinensis (n=2), and Candida keyfr (n=1). Organisms that were found on culture that were not detected by both GenMarkDx ePlex BCID-FP panel and Biofire BCID panel were Candida nivariensis (n=2), Pichia ohmeri (n=1), Trichospon species (n=2).

Conclusion: Based on these data, we expect that the ePlex would have correctly identified 95.9% of the yeasts in this patient population. This represents an additional 18 (13%) of specimens that could be detected rapidly from the positive blood culture if the GenMarkDx ePlex BCID-FP panel were used instead of the Biofire BCID panel.  Early identification can influence the choice of antifungal agent .  Less than 5 % of the yeasts would have remained unidentified by ePLex compared to 13% for Biofire.