414. Diagnostic Usefulness of Differential Time to Positivity (DTP) in Neutropenic Cancer Patients With Suspected Catheter-Related Candidemia (CRC)

BACKGROUND: The decision of catheter removal in neutropenic patients with candidemia is difficult because they usually have surgically implanted catheter, and CRC are less frequent than in non-neutropenic patients. However, there are limited data on distinguishing CRC from non-CRC before catheter removal. We thus evaluated the diagnostic performances of DTP to diagnose CRC in neutropenic cancer patients with suspected CRC. METHODS: All adult neutropenic cancer patients with candidemia were enrolled in a tertiary care hospital from July 2012 to December 2016. Definite CRC was defined if ≥15 CFU of Candida spp. in a removed catheter tip. Probable CRC was defined if (1) one to 14 CFU in catheter tip, and clinical improvement within 48 hours after catheter removal with antifungal agent therapy or (2) the infection was refractory to antifungal therapy alone but improved within 48 hours after catheter removal. Non-CRC was defined if any of the following conditions were satisfied: (1) catheter tip cultures were negative and a noncatheter source of candidemia was found by culture, (2) the catheter tip cultures within 24 h before the start of antifungal therapy were negative, or (3) the clinical improvement before or without catheter removal. If the above conditions are not met, they were grouped into indeterminate, and were excluded from the final analysis. We defined the DTP as the difference in the time to positivity between blood cultures drawn simultaneously from the central vein and a peripheral vein. RESULTS: A total of 35 neutropenic patients with candidemia were enrolled. Of these, 15 patients (43%) with CRC (6 definite and nine probable) and 17 (48.5%) with non-CRC were finally analyzed, excluding threeindeterminate candidemia. On the basis of the receiver operating characteristics (ROC) curve, the optimal cut-off was ≥1.45 hours and the area under the ROC curve was 0.89 (95% CI, 76 to 100) in diagnosing CRC. Of the 15 patients with CRC, 11 (73%) revealed positive DTP, whereas none of the 17 patients with non-CRC exhibits positive DTP. The sensitivity and specificity of DTP for the diagnosis of CRC were 73% (95% CI, 58 to 94) and 100% (95% CI, 71 to 100), respectively. CONCLUSION: DTP appears to be useful to rule in CRC and DTP ≥ 1.45 hours to be the optimal cut-off for CRC in neutropenic cancer patients. DISCLOSURES: All authors: No reported disclosures.