Immature Platelet Fraction as a Sensitive Biomarker in Neonatal Sepsis: Diagnostic Performance Preceding Thrombocytopenia.

: Early and accurate diagnosis of neonatal sepsis remains a clinical challenge due to nonspecific signs and limitations of conventional biomarkers. The immature platelet fraction (IPF), a novel hematologic parameter reflecting thrombopoietic activity, has emerged as a potential early sepsis indicator. This study aimed to evaluate the diagnostic value of IPF in neonatal sepsis prior to the onset of thrombocytopenia. : This prospective study enrolled neonates with early-onset sepsis (EOS), late-onset sepsis (LOS), and healthy controls. IPF, C-reactive protein (CRP), procalcitonin (PCT), and hematologic indices were measured at diagnosis and 48-72 h post-treatment. Diagnostic performance was evaluated via ROC curve analysis, and correlations between IPF and inflammatory/hematologic markers were examined. IPF levels were also compared based on blood culture results. : IPF levels were significantly higher in both EOS (n: 56) and LOS (n: 50) groups compared to controls (n: 44) ( < 0.001). ROC analysis showed excellent diagnostic performance, with AUCs of 0.98 (EOS) and 0.99 (LOS). Following antibiotic treatment, IPF levels declined significantly ( < 0.001), supporting its dynamic value. Strong and moderate correlations were found with MPV and CRP, respectively, and an inverse association with platelet count, but not with PCT. Moreover, IPF levels were higher in culture-positive cases compared to culture-negative ones (13.1% vs. 9.8%; = 0.017) and exhibited diagnostic performance comparable to CRP in predicting blood culture positivity. : This study presents original and clinically relevant data supporting IPF as a promising and practical hematologic biomarker for early detection and treatment monitoring of neonatal sepsis. Its integration into standard sepsis evaluation protocols may improve early risk stratification and clinical decision-making in neonatal intensive care settings.