Accuracy of CD64 expression on neutrophils and monocytes in bacterial infection diagnosis at pediatric intensive care admission

The CD64 receptor has been described as an interesting bacterial infection biomarker. Its expression has not been studied in previously healthy children admitted to pediatric critical care unit (PICU). Our objective was firstly to describe the CD64 expression and secondly study its diagnostic accuracy to discriminate bacterial versus viral infection in this children. We made a prospective double-blind observational study (March 2016-February 2018). A flow cytometry (FC) was done from peripheral blood at PICU admission. We studied the percentage of CD64+ neutrophils and the CD64 mean fluorescence intensity (MFI) on neutrophils (nCD64) and monocytes (mCD64). Statistical analyses were performed with non-parametric tests (p<0.05). Twenty children in the bacterial infection group (BIG) and 25 in the viral infection group (VIG). Children in BIG showed higher values of CD64+ neutrophils (p=0.000), nCD64 (p=0.001), and mCD64 (p=0.003). In addition, CD64+ neutrophils and nCD64 expression have positive correlation with procalcitonin and C reactive protein. The nCD64 area under the curve (AUC) was 0.83 (p=0.000). The %CD64+ neutrophils showed an AUC of 0.828 (p=0.000). The mCD64 AUC was 0.83 (p=0.003). The nCD64 and %CD64+ neutrophils also showed higher combined values of sensitivity (74%) and specificity (90%) than all classical biomarkers.In our series CD64 expression allows to discriminate between bacterial and viral infection at PICU admission. Future studies should confirm this and be focused in the study of CD64 correlation with clinical data and its utility as an evolution biomarker in critical care children.