Time to Positivity as a Prognostic Tool in the Performance of Short-Term Subculture for MALDI-TOF MS-Based Identification of Microorganisms from Positive Blood Cultures in Pediatric Patients

The present study aimed to investigate the relationship between the time to positivity (TTP) of blood cultures and the performance of short-term subculture for MALDI-TOF MS-based identification of microorganisms from positive blood cultures in pediatric patients. The study was conducted between April 2018 and July 2019 at a tertiary children's hospital in Eastern China and the TTP of all the blood cultures included was retrospectively collected at the same time . In total, 332 monomicrobial blood cultures were included in the study. Blood cultures that were identified at the genus level (score ≥ 1.700) by the short-term subculture protocol had shorter TTP (median TTP: 17.5 h) than of those not identified (median TTP: 24.6 h; P < 10 –3 ). Those that were identified at the species level (score ≥ 2.000) by the short-term subculture protocol also had shorter TTP (median TTP: 16.7 h) than of those not identified (median TTP: 21.7 h; P < 10 −3 ). ROC curve analysis indicated that the TTP cutoff value to the genus level of the short-term subculture protocol was 18.2 h (area under the curve (AUC): 0.801; 95% confidence interval (CI) 0.741–0.861; P < 10 −3 ). At the same time, the TTP cutoff value to the species level of the short-term subculture protocol was 18.1 h (AUC: 0.747; 95% CI 0.694–0.800; P < 10 −3 ). TTP is a convenient and valuable prognostic tool for the determination of the performance of short-term subculture for MALDI-TOF MS-based identification of microorganisms from positive blood cultures in pediatric patients.