In this study, all severely deficient participants with < 10% G6PD activity) had 85% or more cells deficient in G6PD activity as determined by flow cytometry. Participants with < 30% G6PD activity had 67% or more cells
deficient in G6PD activity. These discrepancies most likely arise as a consequence of the differences in platforms (microscopy versus flow cytometry) and analysis algorithms. Additional development of the cytochemical methodologies could provide a powerful tool for analysis of G6PD activity level and susceptibility to oxidative challenges.