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GLUCOSE-6 PHOSPHATE DEHYDROGENASE (G6PD), QUANTITATIVE

Item Value
Available Stat? No
Test code GPDQ
Note: CBC (CDP) must be ordered at the same time.
Performed by? Chemistry
Sendout? no
Price range $
In House Availability M, W, F
Principle

G6PD catalyzes the hydrogen transport reaction:

                                   G6PD
Glucose-6-Phosphate + NADP         <-->          6-Phosphogluconate + NADPH + H+

                                  PGD
6 Phosphogluconate + NADP        <-->       ribulose-5-phosphate + NADPH + H+

The rate of formation of NADPH, which absorbs strongly at 340 nm, is utilized as a measure of 
enzyme activity.  An inhibitor is added to the reaction to prevent the formation of the 2nd 
mole of NADPH.



Interpretation The enzyme G6PD catalyzes the reaction that takes place when glucose-6-phosphate is converted to 6-phosphogluconic acid. In carbohydrate metabolism, this enzyme introduces the reaction that starts the pentose phosphate pathway. For this reason, under certain conditions of oxidative stress, an active and adequate concentration of G6PD is necessary in the red cell. G6PD deficiency is associated with the occurrence of hemolytic anemia; patients usually become anemic when exposed to certain drugs or fava beans. Patients with G6PD deficiency may have a hemolytic crisis when drugs of the following types are taken:

1. analgesics or antipyretics, such as aspirin;
2. sulfa drugs, such as sulfapyridine or sulfisoxazole;
3. antimalarials, such as primaquine, pentaquine;
4. other drugs such as chloromycetin, PAS, quinidine (nitrofurantoin or nitrofurazone), dapsone.

Conditions such as viral hepatitis and diabetic acidosis also have been shown to induce hemolytic anemia in patients with G6PD deficiency. Spontaneous hemolysis usually does not occur in newborns with G6PD deficiency.

The administration of an offending drug to a mother with a G6PD deficient fetus, prior to delivery, is considered hazardous.
Container type EDTA (lavender top) tube
Amount to Collect 1 mL
Sample type Whole blood
Special instructions PEDIATRIC SPECIMEN: 1 mL whole blood in lavender top or 0.5 mL by heelstick into capillary whole blood container. (minimum: 0.15 mL for G6PD + 0.3 mL for CBC)
Normal range Above 8.0 IU/g hemoglobin
(> 0.518 mU/mol hemoglobin)
Stability 1 week at 2-8°C.
Additional information INDICATIONS: Investigation of hemolytic anemia.
References 1. Deutsch, J.: Maleimide as an inhibitor in measurement of Erythrocyte Glucose-6-Phosphate Dehydrogenase activity. Clin Chem, 2416:885, 1978.

2. Kornberg, A., and Horecker, B.L. (Calowick, S.P. and Kaplan, N.O., eds), in Methods in Enzymology, Academic Press, Inc., New York (1974), p. 323.

3. Lohr, G.W. and Waller, H.D. (Bergmeyer, H.U., ed.), in Methods in Enzymology, 2nd English ed., Academic Press, Inc., New York (1974), p. 636.

4. Trinity Biotech USA, St. Louis, MO.
CPT coding 82955
Last Updated 10/20/2012 10:04:40 AM
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