Background: Early detection and treatment of infected preterm infants could decrease morbidity and mortality. Neutrophil CD64 has been shown to be an excellent early diagnostic biomarker of late-onset sepsis (LOS) and necrotizing enterocolitis (NEC). We aimed to study whether using CD64 as a daily surveillance biomarker could predict LOS/NEC before clinical manifestation.
Methods: We collected 0.1 mL whole blood from very low birth weight (VLBW) infants from day 7 postnatal age until routine daily blood tests were no longer required. Four categories of responses were defined: proven sepsis, clinical sepsis, nonsepsis/non-NEC, and asymptomatic CD64 activation.
Results: A total of 146 infants were consecutively recruited and 155 episodes of sepsis evaluation were performed. The biomarker screening utility, sensitivity, specificity, positive predictive value, and negative predictive value for surveillance of LOS/NEC using a cutoff of 5655 antibody-PE (phycoerythrin) molecules bound/cell were 89%, 98%, 41%, and 99.8%, respectively. LOS/NEC was detected a mean of 1.5 days before clinical presentation. However, 63 episodes of CD64 activation occurred in asymptomatic infants who would not otherwise have required sepsis evaluations.
Conclusions: As a surveillance biomarker, neutrophil CD64 detected LOS/NEC 1.5 days before clinical presentation, but at the expense of performing 41% additional sepsis evaluations. This was mainly attributed to an unexpected group of asymptomatic infants with CD64 activation, who recovered spontaneously and did not require antimicrobial treatment. The latter group has not been previously recognized in VLBW infants and could represent subclinical infection secondary to transient bacterial translocation or mild viral infection.