Glycogen Storage Disease Type II, Pompe disease : Alpha-glucosidase Enzyme Analysis

Test Information

This biochemical test is a quantitative measurement of alpha-glucosidase enzyme activity can be used as a 1st tier test for patients with a clinical suspicion of Glycogen Storage Disease Type II, Pompe disease. Demonstration of deficient alpha-glucosidase enzyme activity is considered the gold standard to confirm a diagnosis of Glycogen Storage Disease Type II, Pompe disease.

In addition, it can be used to clarify molecular findings in the GAA gene, and to follow up abnormal newborn screening results.

Turnaround Time

2 weeks

CPT Code(s)

82657

Cost

$200


Enzymes

Alpha-glucosidase

Clinical Information

Pompe disease is caused by a deficiency of the enzyme alpha-glucosidase (GAA), an enzyme that at normal levels will breakdown glycogen in the body. Infantile-onset Pompe disease is characterized by hypotonia, generalized muscle weakness and hypertrophic cardiomyopathy. Death generally occurs within the first year of life due to cardiac and respiratory failure. The later-onset form shows greater variability with a slowly progressive muscle weakness and respiratory insufficiency. The degree of enzyme deficiency is generally related to the severity and age of onset.

Indications

This test can be used to confirm a suspected Pompe disease diagnosis. Prenatal diagnosis and carrier testing via enzyme analysis are not available.

Methodology

4-methylumbelliferyl substrate

Specimen Requirements

Enzyme activity can be measured in leukocytes, cultured fibroblasts, or dried blood spots. For leukocytes, please send 5-10 ml of whole blood in a green top (sodium heparin) tube. For dried blood spot collection, a minimum of three circles need to be filled in. Each circle should contain one drop of blood (about 100 microliters). See the link below for additional sample collection and handling instructions.

Transport Instructions

Whole blood samples (for leukocyte analysis) should be shipped at ambient temperature and must arrive at the laboratory within 24 hours of blood draw. Cultured fibroblasts can be sent overnight at room temperature.
For a dried blood spot: When the sample has dried 3-4 hours, fold cover at score line, over sample, and tuck into flap. Ship at ambient temperature.

Have Questions Need Support?

Call our laboratory at 1-800-473-9411 or contact one of our Laboratory Genetic Counselors for assistance.
Robin Fletcher, MS, CGC
Kellie Walden, MS, CGC

Biochemical Testing, Enzyme Analysis, Individual Enzyme Assays, Newborn Screening Follow-Up
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