Implementation of flow cytometry technique for evaluation of neutrophil phagocytic activity in clinical laboratory practice

Recently, flow cytometry (FC) has been used both for scientific purposes and in routine laboratory practice. The range of tasks solved by the FC technique is constantly expanding, and flow cytometry is currently used not only for the diagnosis of hemoblastoses and evaluation of therapeutic efficiency, but also is a promising method for analyzing functions of various cell populations, including blood neutrophils, which play a role in pathogenesis of different immunodeficiency conditions accomplished by recurrent bacterial infections. This work concerns implementation of an FC-based method for determining phagocytic activity of neutrophil granulocytes into laboratory practice. In the course of this study, this test was compared with a traditional technique used in laboratories, i.e., simple visual assessment of phagocytosis reaction of baker’s yeast in suspension. Determining the phagocytic activity of neutrophils by means of flow cytofluorimetry proved to be more reproducible and easily controlled when compared to simple visual assessment technique. We have found that the results of studying the phagocytosis parameters measured by FC-based technique were not influenced by gender and age of the patients. Therefore, uniform ranges for the reference intervals were calculated for different categories of patients. Clinical testing of the FC-based method for determining phagocytic activity of neutrophils was performed in a group of patients suffering from recurrent bacterial infections. Assessment of phagocytic activity by FC approach enabled us to identify a patient with phagocytosis deficiency. Meanwhile, the method of simple visual phagocytosis with a suspension of baker’s yeast showed inferior sensitivity in this case, and the obtained indices of neutrophils’ phagocytic activity did not exceed the reference intervals. Thus, the FC-based method of determining phagocytic activity of neutrophils using FC approach is preferable when used in routine laboratory practice as compared with the method of simple visual assessment of baker’s yeast phagocytosis.