OBJECTIVE AND DESIGN: The aim of this study was to assess the value of procalcitonin (PCT), C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-a), interleukin (IL)-1b, IL-8, and soluble TNF receptor II (sTNFRII) in early and rapid diagnosis of infection in neutropenic children with acute lymphoblastic leukemia (ALL) and to distinguish bacterial from viral infections.PATIENTS: The study included five groups (A, B, C, D, and E) of children with ALL undergoing intensive chemotherapy. Groups A and B consisted of neutropenic children with bacterial and viral infection, respectively. Groups C and D consisted of nonneutropenic children with bacterial and viral infection, respectively. Group E consisted of children without neutropenia and without fever.METHODS: In all groups, blood samples were collected upon admission and then for 7 days on a daily basis. Levels of CRP, PCT, TNF-a, IL-1b, IL-8, and sTNFRII were determined in all blood samples.RESULTS: We found a highly significant difference in PCT levels between bacterial and nonbacterial episodes. Sensitivity and specificity of PCT were 94 and 96.5%, respectively.CONCLUSIONS: Serial measurement of PCT levels on a daily basis seems to be helpful for early prediction of severe bacterial infections, monitoring febrile episodes regarding response to antibiotic therapy, and early detection of complications in the infectious process.