Evaluation of CD64 Expression on Neutrophils as an Early Indicator of Neonatal Sepsis

Background: Enhanced neutrophil CD64 (nCD64) expression is likely to be useful in diagnosis of neonatal sepsis. This study evaluated the diagnostic efficacy of nCD64 expression as an early indicator of neonatal sepsis. Methods: Sixty neonates (culture positive, 24; negative, 36) with suspected sepsis and 30 controls were studied prospectively. CD64 expression was evaluated flow cytometrically on neutrophils and monocytes. Mean and median nCD64 expression, mean and median monocyte CD64/nCD64 (M/N CD64) ratios were computed. Results were correlated with blood culture and other conventional indices of sepsis. Results: The sick neonates had significantly higher mean and median nCD64 expression compared with controls. Monocyte CD64 values did not differ significantly among the groups. Both mean and median M/N CD64 ratios were significantly lower in the former group. Culture-positive neonates had significantly higher mean and median nCD64 values and significantly lower mean and median M/N CD64 ratios than clinically indistinguishable but culture-negative neonates. Both groups were significantly different with respect to these indices from normal controls. Median M/N CD64 ratio was the best discriminant by virtue of highest area under the receiver operator characteristic curve (0.903), with sensitivity and specificity of 91.7% and 88.9%, respectively. Conventional indices were inferior, both singly and in combination. Conclusions: Enhanced nCD64 reported as median M/N CD64 ratio is a highly sensitive marker of culture-positive neonatal sepsis. It additionally identifies a separate group among culture-negative sick neonates and may be useful to guide antibiotic administration especially in these neonates.