Glucose-6-Phosphate Dehydrogenase, (G-6-PD), Quantitative

Message
LIMITED STABILITY PROCESS
Must be collected Sun-Thursday to arrive at QNI Mon-Fri ONLY.


Test Code
G6PD


Quest Code
500


Alias/See Also
500


CPT Codes
82955

Preferred Specimen
1 mL whole blood collected in an EDTA (lavender-top) tube


Minimum Volume
0.5 mL


Other Acceptable Specimens
EDTA (royal blue-top) tube


Transport Temperature
Refrigerated (cold packs)


Specimen Stability
Room temperature: 48 hours
Refrigerated: 7 days
Frozen: Unacceptable


Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Received frozen


Methodology
Kinetic

Setup Schedule
Night Sets up 5 days a week.


Reference Range
7.0-20.5 U/g Hgb


Clinical Significance
Glucose-6-phosphate dehydrogenase (G6PD) deficiency is the most common enzyme deficiency in the world, affecting an estimated 400 million people worldwide [1]. It is more common in people of African, Mediterranean, and Asian descent. G6PD deficiency is an X-linked genetic disorder and, in general, affects males more than females. Severity ranges from mild to severe subtypes. Newborns with G6PD deficiency may have prolonged and more pronounced neonatal jaundice than other newborns. Adults with G6PD deficiency may have episodes of acute hemolytic anemia, and symptoms may include jaundice, fatigue, splenomegaly, and dark urine. Episodes may be induced by illness (infections), certain foods (fava beans), and particular medications (for example some sulfonamides and antimalarial drugs)[2]; therefore, some precautions may be recommended to avoid offending triggers.

Quantitative Glucose-6-Phosphate Dehydrogenase is an assay that measures the G6PD enzyme level. A low value may indicate G6PD deficiency (as opposed to values either within or above the reference range). [Perkins[3]] has found that some females with G-6-PD deficiency have difficulty in carrying a pregnancy to term. Erythrocytic G-6-PD appears to be sensitive to the endocrine changes associated with pregnancy. [Vergnes and Clerc [4]] found that 65% of their patients showed a significant fall in the G-6-PD activity in the later months of pregnancy with return to normal after delivery. Of note, as reticulocytes have higher G6PD activity than mature erythrocytes, if the blood sample is collected just after an acute hemolytic episode, G6PD activity levels can be falsely normal [5]. Therefore, if G6PD deficiency is suspected, consider repeating the test. Molecular genetic testing may also be indicated in cases where the disorder is suspected, or where there is a family history of G6PD deficiency, as enzyme activity may be normal in heterozygous females.

References
1. https://www.who.int/malaria/mpac/mpac-october2019- session7-updating-G6PD-classification.pdf
2. Luzzatto L, Nannelli C, Notaro R. Glucose-6-Phosphate Dehydrogenase Deficiency. Hematol Oncol Clin North Am. 2016 Apr;30(2):373-93.
3. Perkins, R. The significance of glucose-6-phosphate dehydrogenase deficiency in pregnancy. Amer. J Obstetr. And Gynec. 1976. May;125(2):215-223.
4. Vergnes, H and Clerc, A. Erythrocyte Enzyme Activity in Pregnancy. Lancet 1968 Oct;292(7572):834.
5. Frank J. Diagnosis and Management of G6PD Deficiency. Am Fam Physician. 2005 Oct;72(7):1277-82.


Performing Laboratory
Quest Diagnostics Nichols Institute
33608 Ortega Highway
San Juan Capistrano, CA 92690-6130



The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.