Ö. The predictive value of procalcitonin, C-reactive protein, presepsin, and soluble-triggering receptor expressed on myeloid cell levels in bloodstream infections in pediatric patients with febrile neutropenia. Turk J Pediatr 2019; 61: 359-367. The present study investigates the predictive value of procalcitonin (PCT), C-reactive protein (CRP), presepsin (PRE-SEP) and soluble-triggering receptor, as expressed on myeloid cells (sTREM-1) levels in bloodstream infections in pediatric patients with febrile neutropenia. A total of 47 episodes of febrile neutropenia that developed in 30 children with malignancy were analyzed in this study, while the control group comprised 27 children who had undergone chemotherapy for malignancy (completed ≥2 years ago) without neutropenia, fever or drug use. Median PCT, CRP, PRE-SEP and sTREM-1 levels on admission were found to be significantly higher in the patient group than in the control group, while in the blood cultures, the microbiological agent was isolated in 13 (27.7%) of the 47 episodes. Median PCT and CRP levels on days 1, 2 and 7 were higher in the blood culture-positive episodes than in the blood culture-negative episodes. There was no significant difference in the PRE-SEP and sTREM-1 levels on days 1, 2 and 7 between the blood culture-positive and blood culture-negative episodes. The results of the study suggest that PRE-SEP and sTREM-1 are at measurable levels upon admission in children with febrile neutropenia, but that these markers may not be appropriate for the predicting of bloodstream infections, although CRP and PCT levels within the first 24 hours may serve as a guide for clinicians.