|Values are valid only on day of printing.|
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.
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.
> or =12 months: 8.8-13.4 U/g Hb
Reference values have not been established for patients who are <12 months of age.
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