Establishment of the reference intervals of whole blood neutrophil phagocytosis by flow cytometry

OBJECTIVE: To investigate the reference intervals (RIs) of the whole blood neutrophil phagocytosis by flow cytometry (FCM) and to study the application value of neutrophil phagocytosis in infectious diseases. METHODS: Pathogens (Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923) cultured for 18-24 h were labeled by fluorescence probe carboxyfluorescein diacetate succinimidyl ester (CFDA-SE), and then incubated with whole blood at 37℃. The phagocytosis of pathogens by neutrophils was detected by flow cytometry, and a reference interval was established. RESULTS: In the healthy adults, the reference interval for the neutrophil phagocytosis to Escherichia coli was 46.91%-83.09% and to Staphylococcus aureus was 33.92%-69.48%. This method showed good reproducibility. Neutrophil phagocytosis was negatively correlated with the neutrophil count, neutrophil percentage, and neutrophil-to-lymphocyte ratio (NLR, p < 0.05). CONCLUSION: We have successfully established the RIs of neutrophil phagocytosis in whole blood in healthy adults by flow cytometry (FCM), which might be of important clinical value in the diagnosis, treatment, and prognosis of infectious diseases.