CD64 as a diagnostic marker for bacterial infection in acute bronchiolitis

Objectives: The aim of this study was to determine the association between neutrophils and monocytes CD 64 molecules and cases of bronchiolitis with an associated bacterial infection. Methods: Blood samples were obtained from patients younger than 2 years old diagnosed with bronchiolitis. Complete blood count (CBC), blood culture, procalcitonin, and CD64 surface expression in neutrophils and monocytes were examined using flow cytometry. We also assessed CBC, procalcitonin, and CD64 levels in neutrophils and monocytes in 31 healthy control subjects. Results: Sixty-two patients with lower respiratory tract infections were included in the first group. The patients were divided into 34 with non-bacterial infections and 28 with possible bacterial infections. We found a significant increase in the number of positive cells in the Mean Fluorescence Intensity (MFI) of both nCD64 and mCD64 in the Possible Bacterial Infection (PBI) group. Procalcitonin levels correlated with nCD64 and nCD64%, but not with mCD64. The AUC of nCD64 was 0.873 (at a cut-off point of 4489.4; the MFI had a specificity of 73% and a sensitivity of 94%). Conclusion: Neutrophil CD64 may be a marker for bacterial infection in children with bronchiolitis.