In spite of advances in neonatal care and the new generation of antibiotics, neonatal sepsis is still a major cause of morbidity and mortality. Early diagnosis of neonatal sepsis is difficult because clinical signs are non-specific. Thus, new biomarkers are still needed for diagnosis. Gelsolin is an actin-binding plasma protein. Furthermore, extracellular gelsolin binds lipopolysaccharide and lipoteichoic acid, which are major virulence factors of Gram-negative and Gram-positive bacteria. The result of this binding is the inhibition of gelsolin's F-actin depolymerizing activity. Thus, gelsolin inhibits the release of IL-8 from human neutrophils subjected to lipoteichoic acid, lipopolysaccharide and heat-inactivated bacteria treatment. Our hypothesis is that pGSN levels decrease in neonatal infants with sepsis and this decrease might be used as a reliable biological marker. Forty patients who were diagnosed with severe sepsis at a neonatal intensive care unit were enrolled in the sepsis group. Twenty patients who were followed for prematurity were enrolled in the control group. The pGSN level at the time of diagnosis in the sepsis group was 33.98 +/- 11.44 mu m/ml, which was significantly lower than that of control group (60.05 +/- 11.3 mu g/ml, P < 0.001) and after treatment (53.38 +/- 31.26 mu g/ml, P = 0.003). Area under ROC curve was 0.96 (p: 0.0001, 95% CI; 0.90-0.99). Sensitivity was 90.32 (95% CI; 74.2-97.8), specificity was 95 (95% CI; 75.1-99.2). Plasma gelsolin significantly decreased in septic patient and recovery of decreased gelsolin levels correlated with clinical improvement. Thus, plasma gelsolin may be a usable marker for severe sepsis. (C) 2016 Elsevier Ltd. All rights reserved.