Objective To evaluate the expression of CD64 and CD163 on neutrophils and monocytes in the systemic inflammatory response syndrome (SIRS) with/without sepsis and to compare the diagnostic accuracy (area under the curve; AUC) of CD64 and CD163 molecule expression determined as mean fluorescence intensities (MFI) and the ratio (index) of linearised MFI to the fluorescence signal of standardised beads.

Methods Fifty-six critically ill neonates and children, classified as SIRS with sepsis (n  =  29) and SIRS without sepsis (n  =  27). CD64 and CD163 expression was measured by flow cytometric analysis.

Results CD64 and CD163 MFI measured on neutrophils and monocytes were elevated in patients with SIRS and sepsis at day 0 and 24 h (day 1). The AUC of indexes was equal to AUC of MFI for CD64 on neutrophils and monocytes and CD163 on neutrophils (p>0.05 for all comparisons), but not for CD163 on monocytes (see table).

Conclusion CD64 MFI, CD163 MFI, CD64 indexes for neutrophils and monocytes and CD163 index for neutrophils can all be used for discrimination of SIRS and sepsis in critically ill neonates and children. CD64 index for neutrophils, however, is superior to all other markers.