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Test ID G6PD Glucose-6-Phosphate Dehydrogenase (G-6-PD), Quantitative, Erythrocytes

Reporting Name

G-6-PD, QN, RBC

Useful For

Evaluation of individuals with Coombs-negative nonspherocytic hemolytic anemia

 

Rapid testing to assess glucose-6-phosphate dehydrogenase (G6PD) enzyme capacity prior to Rasburicase therapy

Specimen Type

Whole Blood ACD-B


Specimen Required


Container/Tube:

Preferred: Yellow top (ACD solution B)

Acceptable: EDTA

Specimen Volume: 6 mL

Collection Instructions: Do not transfer blood to other containers.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Whole Blood ACD-B Refrigerated 20 days

Reference Values

≥12 months: 8.8-13.4 U/g Hb

Reference values have not been established for patients who are <12 months of age.

Day(s) and Time(s) Performed

Monday through Saturday

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82955

LOINC Code Information

Test ID Test Order Name Order LOINC Value
G6PD G-6-PD, QN, RBC 32546-4

 

Result ID Test Result Name Result LOINC Value
G6PD_ G-6-PD, QN, RBC 32546-4

Clinical Information

Hemolytic disease may be associated with deficiency of erythrocyte enzymes. The most commonly encountered is a deficiency of glucose-6-phosphate dehydrogenase (G6PD).

 

The G6PD locus is on the X chromosome and, thus, G6PD 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 G6PD are known, and the clinical and laboratory features of G6PD deficiency vary accordingly. With some variants, there is chronic, life-long hemolysis, but much more commonly, the condition is asymptomatic and only results in susceptibility to acute hemolytic episodes, which may be triggered by some medications, ingestion of fava beans, viral, or bacterial infections.  It is also associated with neonatal  hyperbilirubinemia.

 

The major G6PD variants occur in specific ethnic groups. Thus, knowledge of the ethnic background of the patient is important. G6PD deficiency has very high frequency in Southeast Asians and is the most common cause of hemolytic disease of the newborn in Southeast Asian neonates.  It is also seen in persons of African and Mediterranean descent.

 

Rasburicase therapy is contraindicated in patients with G6PD deficiency. Deficiency can be assessed by enzymatic and/or genetic assays. If deficient status can be unambiguously assigned by genotyping, that is sufficient. However, due to the limitations of genetic testing, in most cases it is necessary to perform G6PD enzyme testing to assign G6PD status (adapted from Relling et al).(1)

Interpretation

Abnormal values are usually 0% to 20% of normal mean. Intermediate values can occur in some genetic variants and in female carriers.

Clinical Reference

1. Relling MV, McDonagh EM, Chang T, et al: Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines for rasburicase therapy in the context of G6PD deficiency genotype. Clin Pharmacol Ther 2014 Aug;96(2):169-174

2. 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

Analytic Time

1 day

Method Name

Kinetic Spectrophotometry (KS)

Testing Algorithm

The following algorithms are available in Special Instructions:

-G6PD Genotyping Algorithm for Therapeutic Drug Recommendation

-Newborn Screen Follow-up for Glucose-6-Phosphate Dehydrogenase (G-6-PD) Deficiency

 

For more information, see Newborn Screening Act Sheet Glucose-6-Phosphate Dehydrogenase Deficiency in Special Instructions.

Forms

If not ordering electronically, complete, print, and send a Benign Hematology Test Request Form (T755) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/benign-hematology-test-request-form.pdf)