Neonatal sepsis: A difficult diagnostic challenge Francesco Raimondi ⁎, Teresa Ferrara, Rosalba Maffucci, Paola Milite, Dorothea Del Buono, Pasquale Santoro, Letizia Capasso ed Ernesto Grimaldi Division of Neonatology, Department of Pediatrics and Laboratory Medicine, Università “Federico II,” Naples, Italy article info Article history: Accepted 9 March 2011 Neonatal systemic infection is a leading cause of morbidity and mortality both in industrialized and developing countries. The increasing survival rates of preterm neonates with progres- sively lower gestational age and birth weight have been associated with higher occurrence of sepsis. Stratified by weight, approximately 10% of 1000–1500 g infants and 35% of less than 1000 g babies will receive a diagnosis of sepsis during their neonatal period. Early- onset sepsis is acquired during the first 72 h of life via generally a vertical route. Late-onset sepsis is much more common and infection comes generally from invasive devices and direct contact with parents and healthcare personnel. Sepsis is responsible for roughly 50% of neonatal deaths after 2 weeks of life. Coagulase-negative staphylococci are the prevalent infecting organisms followed by E. coli and multidrug resistant Gram-negative organisms including Klebsiella, Pseudomonas and fungi. Clinical presentation may start from subtle and unspecific signs (temperature instability, feeding intolerance, prolonged jaundice) and lead rapidly to catastrophic events such as death or permanent neurological impairment. Timely diagnosis is a greatly needed research goal. Current laboratory tests (CRP, total whites count, absolute neutrophil count, immature to total neutrophil ratio), individually or in combination, do not reach sufficient specificity and sensitivity. The diagnostic gold standard relies on the microor- ganism isolation, though generally only one out of five sepsis evaluation will result in a positive blood culture. Novel diagnostic tools for neonatal sepsis In recent years a different approach has been attempted in diagnosing sepsis. The VCS technology of the Coulter LH 750 hematology analyzer (Beckman Coulter, Fullerton, CA) can obtain directly data from more than 8000 WBCs using direct current impedance to measure cell volume (V) for accurate size of all cell types, radio frequency opacity to characterize conductivity (C) for internal composition of each cell, and a laser beam to measure light scatter (S) for cytoplasmic granularity and nuclear structure. These data then are used to identify each cell as a neutrophil, lymphocyte, monocyte, eosinophil, or basophil, generating an automated differential count. However, the use of the VCS technology to evaluate morphologic changes within the same cell population, such as the previously described neutrophil changes during acute bacterial infection, has never been well studied. Band forms and other immature granulocytes (metamyelocytes, myelocytes), as well as reactive segmented neutrophils, tend to be larger and have lower nuclear complexity than their normal “resting” counterparts. Therefore, Chaves et al. proposed that the morphologic changes seen in the left-shifted and reactive segmented neutrophils could be analyzed quantitatively by using the Coulter LH 750 with VCS technology. These investigators evaluated the clinical usefulness of these morphologic parameters (also referred to as positional parameters) as possible indicators of an acute infectious process. In a retrospective series of 69 adult septic patients and 35 controls, the mean channel for mean neutrophil volume (MNeV) was significantly increased. With an 150 MNeV cut-off, a specificity of 91% and a sensitivity of 70% was achieved. A different series from the same research group evaluated the usefulness of neutrophil volume distribution width (NDW). This parameter, too, was shown to correlate with a positive blood culture and an NDW cut-off of 23 produced a specificity of 100% and a sensitivity of 69%. Our group conducted the first investigation using the VCS technology in diagnosing late-onset neonatal sepsis. In a prospective series of 120 very low birth weight newborns, a MNeV cut-off of 148 produced a specificity of and sensitivity of in detecting late-onset neonatal sepsis on a single determination. MNeV performed better than any other individual item on the rule out sepsis panel. NDW only gave a specificity of 88% and a sensitivity of 95%. A larger, multicenter study is currently underway to validate the use of positional parameters in screening for neonatal sepsis. Also, positional parameters have a potential role in detecting early-onset sepsis and in guiding the length of antibiotic therapy. Due to the severity of the disease, clinicians eagerly await an answer from this promising field of investigation. Clinical Biochemistry 44 (2011) 463–464 ⁎ Corresponding author. E-mail address: raimondi@unina.it (F. Raimondi). 0009-9120/$ – see front matter © 2011 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved. doi:10.1016/j.clinbiochem.2011.03.030 Contents lists available at ScienceDirect Clinical Biochemistry journal homepage: www.elsevier.com/locate/clinbiochem