Glucose-6-phosphate dehydrogenase (G6PD) quantitative testing is a diagnostic tool used to measure the levels of the G6PD enzyme in the blood. This test is primarily used to diagnose G6PD deficiency, a genetic condition where individuals lack sufficient levels of the G6PD enzyme, which can lead to hemolytic anemia. The results can help healthcare providers assess the severity of G6PD deficiency and determine appropriate treatment options.