Glucose-6-phosphate dehydrogenase (G-6-PD) deficiency is a sex-linked disorder that affects mostly males and causes premature breakdown of RBCs. The major variants occur in specific ethnic groups. In a large group of Black men, the incidence of type A G-6-PD deficiency was found to be 11%. Approximately 20% of Black women are heterozygous. With some variants, there is chronic lifelong hemolysis, but more commonly, the condition is with no systems and results only in susceptibility to acute hemolytic episodes, which may be triggered by certain drugs (especially sulfa drugs), ingestion of fava beans, or viral or bacterial infection. G-6-PD hemolysis is associated with formation of Heinz bodies in peripheral RBCs.

The other two most common types are Mediterranean, which is common in Iraqi, Kurdish, Lebanese, and Sephardic Jewish people and less common in Greek, Italian, Turkish, and North African people, and the Mahidol variant, which is common in Southeast Asian people (22% of males).

G-6-PD screen: G-6-PD detected

Adults: 8.6–18.6 U/g Hb or 0.14–0.31 nkat/g Hb

Children: 6.4–15.6 U/g Hb or 0.11–0.26 nkat/g Hb

Newborns: have values up to 50% higher than adults

If done as a screening test, G-6-PD activity is reported as within normal limits. Different laboratories have different ways of reporting.

To convert U/g Hb to U/mL of RBCs: U/g Hb × 0.34 = U/mL of RBCs

1. Obtain 5 mL of whole blood in two lavender-topped tubes (with EDTA or heparin anticoagulant). Label the specimen with the patient’s name, date and time of collection, and test(s) ordered.

2. Perform a G-6-PD screen and then place on ice in a biohazard bag.

3. Do not centrifuge.

4. Refrigerate.

1. G-6-PD is decreased in:

   1. G-6-PD deficiency (causes hemolytic episodes after exposure to certain drugs and fava beans)

   2. Congenital nonspherocytic anemia

   3. Nonimmunologic hemolytic disease of the newborn (Asian and Mediterranean)

2. G-6-PD is increased in:

   1. Untreated megaloblastic anemia (pernicious anemia)

   2. Thrombocytopenia purpura

   3. Hyperthyroidism

   4. Viral hepatitis

Pretest Patient Care

1. Explain test purpose and procedure. There should be no exercising before tests.

2. Withhold transfusion until after blood samples are drawn (especially with osmotic fragility).

3. Follow guidelines in Chapter 1 for safe, effective, informed pretest care.

1. Marked reticulocytosis may give a falsely high G-6-PD.

2. G-6-PD may be falsely normal for 6–8 weeks after a hemolytic episode, especially in Black patients with the type A variant. Retest after the patient recovers from the episode of anemia.