The G6PD flow-cytometric assay is a reliable tool for diagnosis of G6PD deficiency in women and anaemic subjects

Glucose-6-phosphate dehydrogenase (G6PD) activity is essential for redox equilibrium of red blood cells (RBCs) and, when compromised, the RBCs are more susceptible to haemolysis. 8-aminoquinolines (primaquine and tafenoquine) are used for the radical curative treatment of Plasmodium vivax malaria and can cause haemolysis in G6PD deficient subjects. Haemolytic risk is dependent on treatment dose and patient G6PD status but ultimately it correlates to the number of G6PD deficient red blood cells. The G6PD spectrophotometric assay reliably identifies deficient subjects but is less reliable in heterozygous females especially when other blood conditions are present. In this work we analyzed samples with a range of G6PD phenotypes and haematologic conditions from 243 healthy volunteers of Asian or African-American heritage using both the spectrophotomeric assay and the G6PD flow-cytometric assay. Overall 18.5% of subjects (29.3% of Asian females) presented with anaemia, associated to decreased RBCs volume and/or reticulocytosis; the flow-cytometric assay showed good correlation with the spectrophotometric assay in both normal (R2 0.83-0.90) and anaemic subjects (R2 0.84-0.91) and was less influenced by haemoglobin concentration, number of RBCs and reticulocytosis. This resulted in more precise quantification of the number of G6PD deficient RBCs and presumably higher predictive power of drug induced haemolytic risk.