Neutrophil CD64 has a high negative predictive value for exclusion of neonatal sepsis

Background and aim. Neonatal sepsis is a significant contributor to morbidity and mortality globally. Blood culture is the most reliable method for detection of bacterial infection. However, its sensitivity is low and its use in the diagnosis of bacteraemia is fraught with difficulties. CD64 antigen is up-regulated in neutrophils only when they are activated, and has been shown to be a potential biomarker for infection. The primary objective of this study was quantitation of neutrophil CD64 by flow cytometry in neonates with signs and symptoms suggestive of sepsis/infection in the first 4 weeks of life. Methods and results. In this prospective observational study, patients were classified into categories of infection, namely definite, probable and possible. Of 76 neonates, 1 had definite infection, 5 probable infection, 30 possible infection, and 32 no infection. The neutrophil CD64 index at a cut-off value of 1.8 had a high negative predictive value (95.2%) in ruling out combined probable and definite infection. Conclusions. We recommend inclusion of the neutrophil CD64 index into the diagnostic algorithm for neonatal sepsis, as it has a high negative predictive value and can be used to rule out infection. As the positive predictive value of the index was low in confirming infection, it should be used as a screening rather than a confirmatory test. S Afr J CH 2013;7(1):25-29. DOI: 10.7196/SAJCH.482