G6PD Deficiency

The test is based on the oxidation of glucose-6-phosphate by glucose-6-phosphate dehydrogenase (G-6-PD) contained in the sample. This reaction generates NADPH, the presence of which is quantified by colorimetry using a tetrazolium salt. The signal intensity obtained by measuring absorbance is directly proportional to the G-6-PD activity present in the sample.

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is one of the most common enzyme disorder diagnosed, affecting more than 400 million people worldwide.

G6PD catalyzes the first shunt step of monophosphate hexoses, oxidizing glucose-6-phosphate in 6-phosphogluconolactone and reducing NADP to NADPH. This metabolic pathway is the only erythrocyte source of NADPH, an important cofactor in glutathione metabolism and whose primary function is to protect red blood cells from oxidative damage caused by binding between hemoglobin and oxygen. 

In individuals with a glucose-6-phosphate dehydrogenase deficiency diagnosis, G6PD will therefore lead to a decrease in the concentration of antioxidant agents (NADPH and glutathione) within red blood cells. This leads to excessive oxidation of hemoglobin and other proteins, leading to loss of function and cell lysis.

The clinical spectrum of glucose-6-phosphate dehydrogenase deficiency is broad. The severity of the disease and the probability of developing neonatal jaundice or chronic hemolysis, as well as the extent of hemolysis when hemolytic episodes occur, depend on the degree of enzyme deficiency. Patients are most often asymptomatic, but many individuals may experience episodes of episodic anemia. A few have chronic hemolytic anemia.

Screening is based on a measurement of glucose-6-phosphate dehydrogenase activity on dried blood spots.