Monocyte HLA-DR expression and neutrophil CD64 expression as biomarkers of infection in critically ill neonates and infants.

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BACKGROUNDReduced monocyte HLA-DR expression and increased neutrophil CD64 expression have been proposed as biomarkers of infection.METHODSFrom 2009–2011, blood samples from NICU and pediatric ICU patients <1 year of age were collected at enrollment and during subsequent evaluation for suspected infection, if it occurred. Samples were analyzed for monocyte HLA-DR and neutrophil CD64 expression levels by flow cytometry.RESULTSForty-seven infants had study samples collected at enrollment; twenty-six infants had study samples collected at the time of a suspected infection. At enrollment, there was an inverse relationship between neutrophil CD64 expression and age (p≤0.047). At the time of suspected infection, infants with an infection demonstrated a lower percentage of HLA-DR+ monocytes (p=0.02, AUC 0.78), higher percentage of CD64+ neutrophils (p=0.009, AUC 0.81), and higher neutrophil CD64 expression levels (p=0.04, AUC 0.75).CONCLUSIONMonocyte HLA-DR and neutrophil CD64 expression in critically ill infants are related to age and infection.