Hematologic profile of sepsis in neonates: neutrophil CD64 as a diagnostic marker.

OBJECTIVE: The goal was to determine the utility of neutrophil CD64 as a diagnostic marker for sepsis in neonates.
METHODS: A prospective study that enrolled consecutive infants with suspected sepsis was performed. Complete blood count with differential, blood culture, and CD64 index measurement were performed, and neutrophil CD64 indices were correlated with the diagnoses of confirmed and suspected sepsis.
RESULTS: There were 293 episodes of sepsis evaluations for 163 infants. Infants with sepsis episodes (confirmed or suspected; n = 40) were of greater gestational age (34.7 +/- 0.9 weeks), compared with those (n = 123) with no sepsis (32.6 +/- 0.5 weeks), but had similar birth weights (2325 +/- 200 vs 1969 +/- 94 g) and Apgar scores at 1 and 5 minutes. There was no difference in the duration of hospitalization for the 2 groups. As expected, the hematologic profiles of sepsis episodes (n = 128) were characterized by higher white blood cell counts, absolute neutrophil counts, absolute band counts, and immature/total neutrophil ratios but lower platelet counts. Sepsis episodes had higher neutrophil CD64 indices (5.61 +/- 0.85 vs 2.63 +/- 0.20). For all sepsis episodes, the CD64 index had an area under the curve, in receiver operating characteristic analysis, of 0.74; with a cutoff value of 2.30, the CD64 index in combination with the absolute neutrophil count had the highest negative predictive value (93%) for ruling out sepsis and 95% sensitivity for diagnosing sepsis. For culture-positive sepsis episodes, the CD64 index had the highest area under the curve (0.852) of all hematologic variables, with a sensitivity of 80% and a specificity of 79%, with a cutoff value of 4.02.
CONCLUSIONS: Neutrophil CD64 is a highly sensitive marker for neonatal sepsis. Prospective studies incorporating CD64 into a sepsis scoring system are warranted.