What is the role of lab testing in the diagnosis of glucose-6-phosphate dehydrogenase (G6PD) deficiency?

Updated: Jun 25, 2020
  • Author: Lawrence C Wolfe, MD; Chief Editor: George T Griffing, MD  more...
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Answer

Tests to diagnose hemolysis include the following:

  • Complete blood cell count (CBC) and reticulocyte count
  • Peripheral blood smear
  • Lactate dehydrogenase (LDH) level
  • Indirect and direct bilirubin level
  • Serum haptoglobin level
  • Urinalysis for hemoglobinuria
  • Urine hemosiderin 

Other causes of hemolysis and hemoglobinuria

Tests to rule out other causes of hemolysis and hemoglobinuria include the following:

Complete blood cell count will show mild to severe anemia depending on the G6PD variant and the type of oxidant stress. Increase in reticulocyte count represents bone marrow response to hemolysis by producing young red cells. Increase in indirect serum bilirubin and LDH indicate hemolysis. Low or absent haptoglobin levels, hemoglobinemia, hemoglobinuria, and presence of urinary hemosiderin indicate severe intravascular hemolysis, which is the main contributor to pathophysiology and diagnosis of G6PD deficiency. A part of hemolysis can be extracellular where damaged red cells are recognized as abnormal and undergo extravascular hemolysis by reticulo-enothelial system. [14]

On the peripheral smear, routine staining may reveal polychromasia, representing increased red blood cell production. Another typical feature is the presence of “hemighosts,” red cells that appear to have unevenly distributed hemoglobin, and  “bite cells” or “blister cells,” red cells that appear to have a portion of them bitten away. Blister cells are characteristic of acute hemolysis induced by oxidative stress. [18]

Denatured hemoglobin can be visualized as Heinz bodies in peripheral blood smears processed with supravital staining. Heinz bodies are shown in the figure below.

Heat stability and/or heat denaturation and high-performance liquid chromatography can be used to identify unstable hemoglobin and thereby rule out G6PD deficiency.


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