Monocyte Distribution Width as a Novel Diagnostic Biomarker in Late-Onset Sepsis Among Preterm Neonates

Neonatal sepsis is a major cause of morbidity and mortality among newborns worldwide. It represents a systemic inflammatory response to infection that can rapidly progress to severe complications, including multi-organ dysfunction and death. The clinical presentation is often nonspecific, making early diagnosis challenging and frequently delayed. The diagnosis of LOS relies on a combination of clinical suspicion, microbiological confirmation, and supportive laboratory findings. Blood culture remains the gold standard for diagnosis, as it confirms the infection and identifies the causative organism, allowing for targeted antibiotic therapy. Biomarkers play an essential role in the early detection and management of sepsis. Commonly used biomarkers include C-reactive protein (CRP), an indicator of systemic inflammation and infection. However, these markers have limitations, including delayed elevation, lack of specificity, and variability in sensitivity, especially in neonatal populations. Additional diagnostic tools such as molecular assays (e.g., polymerase chain reaction techniques) have improved the speed of pathogen identification but are not yet universally available. Monocyte distribution width (MDW) is a novel hematological parameter that reflects changes in monocyte size and morphology during inflammatory processes. Monocytes are among the first immune cells to respond to infection, undergoing functional and structural alterations that can be quantitatively assessed through MDW.