Neutrophil CD64 index for diagnosis of infectious disease in the pediatric ICU: a single-center prospective study

Background: Infection is a major cause of death in children, and it is particularly important to identify biological indicators of early infection. Previous studies showed that the neutrophil CD64 (nCD64) index may be a useful biomarker for infection. The purpose of this study was to investigate use of the nCD64 index to identify infection in children from a pediatric ICU (PICU) in China. Methods: This prospective observational study enrolled 201 children who were admitted to our PICU and were divided into an infection group and a non-infection group. In each patient, C-reactive protein (CRP), nCD64 index, procalcitonin (PCT), and white blood cell count were measured during the first 24 h after admission. Receiver operating characteristic (ROC) analyses were used to determine the sensitivity, specificity, and diagnostic value of the nCD64 index for infection. Results: Among all 201 children, the infection group had greater levels of CRP, nCD64 index, and PCT (all p < 0.05). ROC analysis indicated the nCD64 index had a sensitivity of 68.8%, specificity of 90.7%, accuracy of 80.5%, and an optimal cut-off value of 0.14, which had better diagnostic value than CRP or PCT. For children with postoperative fever, the nCD64 index also distinguished systemic inflammatory response syndrome (SIRS) from infection with accuracy of 79%. Conclusions: The nCD64 index is a useful biomarker for the diagnosis of early infection in children admitted to the PICU.