Circulating DNA and Neutrophil-Derived Biomarkers in Neonatal Sepsis

Neutrophil extracellular traps (NETs) contribute to innate immunity in sepsis, but their diagnostic value in neonates is unclear. We evaluated whether circulating NET-associated biomarkers discriminate septic from non-infected neonates. In this prospective observational study 96 neonates (≥34 weeks gestational age) with clinical suspicion of infection were enrolled (36 sepsis, 60 controls). Serum cell-free DNA (cfDNA), myeloperoxidase-DNA complexes (MPO-DNA), neutrophil elastase-DNA complexes (NE-DNA), and citrullinated histone H3 (H3cit) were measured alongside CRP and IL-6 at days 1, 3, and 5. Diagnostic performance was assessed by receiver operating characteristic (ROC) analysis with bootstrap confidence intervals. CRP (AUC 0.75, 95% CI 0.66-0.85) and IL-6 (AUC 0.73, 95% CI 0.61-0.83) showed the best diagnostic performance. cfDNA demonstrated moderate discrimination (AUC 0.72, 95% CI 0.60-0.84) but was only transiently elevated at day 1. MPO-DNA (AUC 0.47), NE-DNA (AUC 0.44), and H3cit (AUC 0.47) performed no better than chance. Within the sepsis group, MPO-DNA and NE-DNA at day 3 strongly correlated with the immature-to-total neutrophil ratio (ρ = 0.76 and 0.72), suggesting these markers reflect neutrophil degranulation rather than NET formation. NET-associated biomarkers do not improve diagnostic accuracy for neonatal sepsis beyond CRP and IL-6. These findings support the concept that neonatal innate immune responses differ fundamentally from adult patterns.