Glucose-6-Phosphate Dehydrogenase (G-6-PD), Quantitative, Erythrocytes
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Hemolytic disease may be associated with deficiency of any 1 of 20 erythrocyte enzymes. The most commonly encountered is a deficiency of glucose-6-phosphate dehydrogenase (G-6-PD).
The G-6-PD locus is on the X chromosome, and thus G-6-PD deficiency is a sex-linked disorder. Affected males (hemizygotes) inherit the abnormal gene from their mothers who are almost always asymptomatic carriers (heterozygotes). More than 300 molecular variants of G-6-PD are known, and the clinical and laboratory features of G-6-PD deficiency vary accordingly. With some variants, there is chronic, life-long hemolysis, but more commonly, the condition is asymptomatic and only results in susceptibility to acute hemolytic episodes which may be triggered by some drugs, ingestion of fava beans, viral, or bacterial infections.
The major G-6-PD variants occur in specific ethnic groups. Thus, knowledge of the ethnic background of the patient is important. G-6-PD deficiency has very high frequency in Southeast Asians and is the most common cause of hemolytic disease of the newborn in Southeast Asian neonates.
Evaluation of individuals with Coombs-negative nonspherocytic hemolytic anemia
Abnormal values are usually 0% to 20% of normal mean.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
In African Americans with the glucose-6-phosphate dehydrogenase (G-6-PD) A-variant, normal values may be measured for several weeks following hemolysis. This is not the case with other G-6-PD variants that predispose to hemolysis.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
> or =12 months: 8.8-13.4 U/g Hb
Reference values have not been established for patients who are <12 months of age.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Beutler E: Glucose-6-phosphate dehydrogenase deficiency. In Hematology. Fifth Edition. Edited by E Beutler, MA Lichtman, BS Coller, TJ Kipps. New York, McGraw-Hill Book Company, 1995, pp 564-586