To diagnose glucose 6 phosphate dehydrogenase there are qualitative tests quantitative tests and cytochemical assays.
In qualitative tests it is distinguished if an individual has G6PD deficiency above or below a certain level and this level is 30% of normal G6PD levels. So if a person has more than 30% of G6PD activity it is considered normal.
In quantitative G6PD test the exact amount of G6PD enzyme activity is measured and it is normalised against the red blood cell count or hemoglobin concentration.
In cytochemical essays the G6PD activity at individual red blood cell level is measured by the through microscope or through flow cytometry analysis.