Glucose-6-phosphate dehydrogenase deficiency Diagnosis

The diagnosis of Glucose-6-phosphate dehydrogenase deficiency is generally suspected when patients from certain ethnic groups develop anemia, jaundice and symptoms of hemolysis, especially when there is a positive family history.

Tests for diagnosed G6PD deficiency will include:

• Complete blood count
• Macrocytosis - due to reduced folic acid which is required for erythropoiesis
• Reticulocyte count - raised; gives indication of the bone marrow activity (bone marrow sampling thus not needed)
• Blood film - acute hemolysis from G-6-PD deficiency can produce Heinz bodies, which are denatured hemoglobin and bite cells
• Hemolysis - reduced levels of haptoglobin and elevated levels of bilirubin; hemoglobinuria
• Direct antiglobulin test - to look for other causes of hemolysis; should be negative in G-6-PD deficiency
• Renal function - to ensure no renal failure as a precipitant
• Liver function tests - to exclude other causes of raised bilirubin
• G-6-PD enzyme activity - is definitive test (as opposed to the amount of G-6-PD protein)
• Performing assays for G-6-PD during haemolysis and reticulocytosis may affect levels and not reflect baseline values
• Ultrasound examination of the abdomen may reveal splenomegaly and gallstones

When there are sufficient grounds to suspect G6PD, a direct test for G6PD is the Beutler fluorescent spot test. The Beutler fluorescent spot test is a rapid and inexpensive test that visually identifies NADPH produced by G6PD under ultraviolet light. When the blood spot does not fluoresce, the test is positive; it can be falsely negative in patients who are actively hemolysing. It can therefore only be done 15-20 days after a hemolytic episode.

When a macrophage in the spleen identifies an RBC with a Heinz body, it removes the precipitate and a small piece of the membrane, leading to characteristic "bite cells". However, if a large number of Heinz bodies are produced, as in the case of G6PD deficiency, some Heinz bodies will nonetheless be visible when viewing RBCs that have been stained with crystal violet.

Newborn screening for G6PD deficiency can be done by enzyme analysis or primary DNA screening test. DNA analysis of the four most common mutations in the U.S. population will identify approximately 90% of individuals with G6PD Deficiency. Confirmatory testing using a quantitative assay should be performed for diagnosis of G6PD deficiency.