The type I Fc receptor for immunoglobulin G (CD64) is a membrane glycoprotein expressed by polymorphonuclear leukocytes (PMNs). Prior studies suggest that increased expression of CD64 may occur during states of acute infection, and therefore may be useful as an early indicator of incipient sepsis. The purpose of this study was to determine whether neutrophil CD64 expression correlated with subclinical and/or overt sepsis in neonates. All neonates admitted to Wilford Hall Medical Center between 1 April 1996 and 31 January 1997 who were being evaluated for suspected sepsis were eligible for this study. After parental consent, blood was obtained at the time of sepsis evaluation and 12-24 hours later, and flow cytometry for neutrophil CD64 expression was performed. Patients were assigned to one of six groups based on clinical status and blood culture results. Group definitions are summarized in the table below.

Table 1 No caption available.
Full size table

No differences in CD64 expression at zero hours were detected among the groups by one-way analysis of variance (p =.745). Similarly, no differences were detected at 12-24 hours (p =.347, group data not shown). In addition, no difference in CD64 expression between the two timepoints could be demonstrated(p =.947, group data not shown). Also, no correlation between CD64 expression and presence/absence of meconium-stained amniotic fluid, nuchal cord, or acidosis at birth was found. Although minimal in the healthy adult, we have shown that CD64 expression varies widely in the neonate, whether healthy or ill. Although the reasons for this phenomenon are unknown, we speculate that it may be a function of the stresses of birth or immaturity of the immune system. Nevertheless, it appears that CD64 expression will not be useful as an indicator of neonatal sepsis.

*symptomatic = any of the following: tachypnea, tachycardia, hyper/hypothermia, hypoglycemia, hypotension, poor feeding, emesis, seizures, lethargy