Background CD64 is expressed on the surface membrane of neutrophils (nCD64) in the presence of bacterial infection. Although initial studies in intensive care settings have been promising, only two small, methodologically flawed studies have been performed in feverish children presenting to the emergency departement (ED), both of which were showing a moderate diagnostic value of nCD64 to detect a serious bacterial infection (SBI). This study aimed to determine the diagnostic value of nCD64 in children presenting with fever to the ED for detecting SBI. Methods In this prospective observational multi-centre study previously healthy children aged 1 month-16 years with fever, presenting to the ED of two hospitals in the Netherlands in 2011-2012 were included. Standardised information on clinical features were collected and nCD64 and CRP were measured routinely. Multivariable logistic regression was used to determine the discriminative ability to detect SBI (ROC-area) of nCD64 compared with CRP. Diagnostic performance measures including sensitivity, specificity and likelihood ratios were calculated. Results In 392 children (45%) with both CRP and nCD64 determined, 52 children (13%) had an SBI. The AUC of the ROC curve for CD64 was 0.62 (95% CI=0.54-0.70) and 0.75 (95% CI=0.67-0.83) for CRP. Neither duration of fever nor deviated vital signs influenced the diagnostic performance of nCD64. Conclusion NCD64 expression has poor discriminative value to detect children with an SBI in a general population of febrile children at the ED. It has no superior value compared to CRP in this setting, neither in total nor in sub-populations.

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Infectious Diseases
Department of Immunology

van Veen, M, Nijman, R.G, Zijlstra, M, Dik, W.A, de Rijke, Y.B, Moll, H.A, … Oostenbrink, R. (2016). Neutrophil CD64 expression is not a useful biomarker for detecting serious bacterial infections in febrile children at the emergency department. Infectious Diseases, 48(5), 331–337. doi:10.3109/23744235.2015.1118156