MONOCYTE HLA-DR EXPRESSION AND NEUTROPHIL CD64 EXPRESSION AS BIOMARKERS OF INFECTION IN CRITICALLY ILL NEONATES AND INFANTS

BACKGROUND: Reduced monocyte HLA-DR expression and increased neutrophil CD64 expression have been proposed as biomarkers of infection. METHODS: From 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. RESULTS: Forty-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). CONCLUSION: Monocyte HLA-DR and neutrophil CD64 expression in critically ill infants are related to age and infection.