258. False Negative Rate of T2Candida Assay in Blood Culture Positive Candidemia

BACKGROUND: The T2Candida (T2C) assay is an FDA-approved, non-culture-based rapid diagnostic that utilizes PCR and magnetic resonance technology to detect candidemia in a whole blood specimen. T2C can detect the 5 most common pathogenic species: C. albicans, C. tropicalis, C. parapsilosis, C. krusei, and C. glabrata. The sensitivity of T2C is reported to be 88–94%, varying by the species, based on the original clinical trial from 2015. Only 6 patients with candidemia were included in the study, so it was supplemented with samples spiked with known quantities of Candida spp. In this study, we sought to evaluate the sensitivity of T2C with routine usage in a tertiary-care academic hospital. METHODS: All patients with a blood culture (BC) positive for Candida spp. during the years 2016 through 2018 were identified. Repeat positive cultures of the same species within 30 days of the initial culture were excluded. We then reviewed the medical records of those patients with a T2C collected ±12 hours from the time of the BC collection. Data collection included demographics, time to antifungal therapy, time to culture reported positive, impact of false negative T2C on antifungal therapy, and 30-day mortality. RESULTS: There were 281 episodes of candidemia (designated as a positive blood culture) in the study period. Forty-four of these episodes had a T2C collected within the specified timeframe (Figure 1). Overall, there were 17 false-negative T2C, reflecting a sensitivity of 61% (27/44). Excluding species not detected by T2C, the sensitivity was 71% (21/38). Of the false-negative group, antifungal therapy was impacted in 8 patients: delayed initiation in 6 patients (1–4 days) and treatment interruption in 2 patients (1 dose each). Demographics, time to treatment, time to culture positivity, and 30-day mortality were similar in the two groups (Table 1). CONCLUSION: In spite of the test being readily available and increasingly used, only 44/281 (16%) of patients with a positive BC had a T2C ordered concurrently. Our experience shows a much lower sensitivity than the clinical trial, in part due to species not detected by T2C. Considering only those organisms on the T2C panel, the false-negative rate was 29%. Impact on treatment was limited to half of the false-negative patients with no difference in mortality. [Image: see text] [Image: see text] DISCLOSURES: All authors: No reported disclosures.