Neutrophil CD64 Is a Sensitive Diagnostic Marker for Early-Onset Neonatal Infection

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Abstract
This prospective study aimed to evaluate the diagnostic utilities of neutrophil CD64 expression for the identification of early-onset clinical infection and pneumonia in term infants and to define the optimal cutoff value so that it may act as a reference with which future studies can be compared. Term newborns in whom infection was suspected when they were <72 h of age were recruited into the study. C-reactive protein (CRP) and expression of CD64 on neutrophils were measured at 0 h (at the time of sepsis evaluation) and 24 h. The sensitivity, specificity, positive predictive value, and negative predictive value (NPV) of CRP, CD64, and the combination of these two markers for predicting neonatal sepsis were determined. A total of 338 infants with suspected clinical sepsis were investigated, 115 of whom were found to be clinically infected. CRP and CD64 in infected infants were both significantly elevated at 0 and 24 h compared with noninfected infants (p < 0.001). The calculated optimal cutoff value for CD64 was 6136 antibody-phycoerythrin molecules bound/cell. CD64 has a very high sensitivity (96%) and NPV (97%) at 24 h. The addition of CRP only marginally enhanced the sensitivity and NPV (97 and 98%, respectively). In conclusion, neutrophil CD64 is a very sensitive diagnostic marker for the identification of early-onset clinical infection and pneumonia in term newborns. The results strongly suggest that measurement of neutrophil CD64 may allow neonatal clinicians to discontinue antibiotic treatment at 24 h in infants who are clinically stable and whose CD64 expressions are below the optimal cutoff level.