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glucose-6-phosphate dehydrogenase (G6PD) in erythrocytes

Indications: - evaluation of G6PD deficiency Contraindications: - do not measure during an acute attack - levels are elevated in erythrocytes [5] Reference values: - Normal is complete decolorization within 20-60 minutes. 5-15 U [5], 12 +/- 2 U/g Hgb [6], 4 +/- 1 U/mL [6] Clinical significance: Three G6PD variants occur with high frequency: 1) G6PD A- is common in blacks (10%) 2) G6PD Mediterranean 3) G6PD Mahidal G6PD variants with severely reduced activity (e.g., Mediterranean & Mahidal) may cause hemolytic disease of the Newborn. A small proportion of persons with G6PD Mediterranean have mild chronic hemolysis. Persons with G6PD Mediterranean are also subject to favism, an acute & very severe hemolytic crisis,often with fatal outcome, precipitated by ingestion of fava beans (Vicia fava). These individuals are also susceptible to severe hemolysis following ingestion of various pharmaceuticals & as a consequence of infections. Hemolysis in blacks with G6PD deficiency is rarely severe or life-threatening. Hemolysis is associated with ingestion 8-aminoquinolines & other pharmaceuticals. 1) antimalarial drugs of the 8-aminoquinoline type - primaquine 2) older sulfonamides such as sulfanilamide 3) sulfones 4) nalidixic acid 5) nitrofurantoin 6) large doses of vitamin C Decreases: - G6PD deficiency Principle: G6PD deficiency is an inborn error of metabolism, or genetic defect, that occurs in 10-15% of American Negroes, & is common in other dark-skinned races. Individuals with a G6PD deficiency will experience an acute hemolytic episode after ingestion of certain drugs & food products. (Example: Primaquine, fava beans). G6PD deficiency is inherited as a partially dominant sex-linked (X chromosome) gene. Affected males usually show full expression (presumably homozygous); females usually show an intermediate expression (heterozygous). An occasional female may show full expression (presumably homozygous). Normally 90% of glucose is broken down through glycolysis, which supplies energy for NADH methemoglobin reductase, an enzyme which converts methemoglobin to hemoglobin. The pentose-phosphate shunt is an alternative pathway in which the enzyme glucose-6-phosphate dehydrogenase enhances the breakdown of glucose-6-phosphate to ribulose-5-phosphate. Concurrent with this breakdown, G6PD generates NADH from NAD which in turn supplies reduccing equivalents for NADH methemoglobin reductase, which also converts methemoglobin to hemoglobin. Specimen: Anticoagulated blood (heparinized or EDTA), a minimum of 0.5 mL G6PD activity in whole blood may decline if sample is refrigerated (2-6 C), but may still fall within the normal range after a week or more at this temperature.

Related

glucose-6-phosphate 1-dehydrogenase (G6PD) glucose-6-phosphate dehydrogenase [G6PD] deficiency; chronic non-spherocytic hemolytic anemia (CNSHA)

General

glucose-6-phosphate dehydrogenase in specimen

References

  1. Reference Procedure for Glucose-6-Phosphate Dehydrogenase (G6PD) Deficiency Test. Sigma Diagnostics Procedure #400, 1989.
  2. Tietz, Norbert W., Ph.D., Textbook of Clinical Chemistry, W.B. Saunders Company, Philadelphia, PA, 1986, p. 1498-1499.
  3. Doxiadis, S.A., Fessas, F.H., Valaes, T., & Mastrokalos, N., Lancet, 297, Feb. 11, 1961.
  4. Medical Laboratory & Clinical Pathology, Sanders, 2nd Edition, Cornbloth & Schwartz, 1966.
  5. Medical Knowledge College of Physicians, Philadelphia 1998, 2018.
  6. Clinical Guide to Laboratory Tests, 3rd edition, NW Tietz ed, WB Saunders, Philadelphia, 1995
  7. Glucose-6-Phosphate Dehydrogenase Laboratory Test Directory ARUP: 80135

Component-of

pyruvate kinase/pyruvate kinase/glucose-6-phosphate dehydrogenase in erythrocytes