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Test ID: PDBS Pompe Disease, Blood Spot


Ordering Guidance


Due to reference range differences, this test is the appropriate test for patients older than 6 weeks of age. For patients 6 weeks of age or younger, order PD2T / Pompe Disease Second-Tier Newborn Screening, Blood Spot.



Specimen Required


Supplies: Card-Blood Spot Collection (Filter Paper) (T493)

Container/Tube:

Preferred: Blood Spot Collection Card

Acceptable: PerkinElmer 226 (formerly Ahlstrom 226) filter paper, Munktell filter paper, Whatman Protein Saver 903 paper, or blood collected in tubes containing ACD, EDTA, or heparin and dried on filter paper

Specimen Volume: 3 blood spots

Collection Instructions:

1. An alternative blood collection option for a patient older than 1 year of age is fingerstick. See Dried Blood Spot Collection Tutorial for how to collect blood spots via fingerstick: https://vimeo.com/508490782 .

2. Completely fill at least 3 circles on the filter paper card (approximately 100 microliters blood per circle).

3. Let blood dry completely on the filter paper at ambient temperature in a horizontal position for a minimum of 3 hours.

4. Do not expose specimen to heat or direct sunlight.

5. Do not stack wet specimens.

6. Keep specimen dry.

Additional Information:

1. For collection instructions, see Blood Spot Collection Instructions in Special Instructions

2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777) in Special Instructions.

3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800) in Special Instructions.


Forms

1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602) in Special Instructions

3. If not ordering electronically, complete, print, and send a Biochemical Genetics Test Request (T798) with the specimen.

Useful For

Evaluation of patients with a clinical presentation suggestive of Pompe disease (muscle hypotonia, weakness, or cardiomyopathy) outside of the newborn screening setting

Method Name

Flow Injection Analysis-Tandem Mass Spectrometry (FIA-MS/MS)

Reporting Name

Pompe Disease, BS

Specimen Type

Whole blood

Specimen Minimum Volume

1 Blood spot

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole blood Refrigerated (preferred) 56 days FILTER PAPER
  Frozen  56 days FILTER PAPER
  Ambient  7 days FILTER PAPER

Clinical Information

Pompe disease, also known as glycogen storage disease type II, is an autosomal recessive disorder caused by a deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA; acid maltase) due to variants in the GAA gene. The estimated incidence is 1 in 40,000 live births. In Pompe disease, glycogen that is taken up by lysosomes during physiologic cell turnover accumulates, causing lysosomal swelling, cell damage and, eventually, organ dysfunction. This leads to progressive muscle weakness, cardiomyopathy, and, eventually, death. Patients with Pompe disease, especially those with infantile, childhood, and juvenile onset, can have elevations of serum enzymes (such as creatine kinase) secondary to cellular dysfunction. Delayed diagnosis of symptomatic patients with later onset Pompe disease is not unusual due to nonspecific and overlapping presentation (such as proximal muscle weakness and respiratory insufficiency) with more common neuromuscular diseases.

 

The clinical phenotype of Pompe disease lies on a spectrum, with differing clinical phenotypes dependent on age of onset and residual enzyme activity. Complete loss of enzyme activity causes onset in infancy leading to death, typically within the first year of life when left untreated. Juvenile and adult-onset forms, as the names suggest, are characterized by later onset and longer survival. All disease variants are eventually associated with progressive muscle weakness and respiratory insufficiency. Cardiomyopathy is associated almost exclusively with the infantile form. Treatment with enzyme replacement therapy is available, making prompt diagnosis of Pompe disease desirable, as early initiation of treatment may improve prognosis.

 

The ratio calculated using the creatinecreatinine ratio as the numerator and the activity of GAA as the denominator can differentiate true cases of infantile and late-onset Pompe disease from false-positive cases such as carriers and pseudodeficiency of GAA enzyme. This determination can be performed in a timely fashion and provide better guidance in the decision to submit samples for further confirmatory testing by molecular genetic analysis (GAAZ / Pompe Disease, Full Gene Analysis, Varies).

Reference Values

An interpretive report will be provided.

Interpretation

An interpretive report (including acid alpha-glucosidase (GAA) activity and [Creatine/Creatinine]/GAA ratio, if applicable) is provided.

 

The quantitative measurements of informative metabolites and related ratios are evaluated using the Collaborative Laboratory Integrated Reports (CLIR) system. The report is in text form only, indicating if the applicable ratio is normal or abnormal and whether or not the CLIR postanalytical tool is informative for Pompe disease. Abnormal results are not sufficient to conclusively establish a diagnosis of a particular disease. To verify a preliminary diagnosis, independent biochemical (ie, in vitro enzyme assay) or molecular genetic analyses are required, many of which are offered by Mayo Clinic Laboratories. Recommendations for additional biochemical testing and confirmatory studies (enzyme assay, biomarker testing, molecular analysis) are provided in the interpretative report.

Clinical Reference

1. Pascual JM, Roe CR: Systemic metabolic abnormalities in adult-onset acid maltase deficiency: beyond muscle glycogen accumlation. JAMA Neurol. 2013 Jun;70(6):756-763

2. Tortorelli S, Eckerman JS, Orsini JJ, et al: Moonlighting newborn screening markers: The incidental discovery of a second tier test for Pompe disease. Genet Med. 2018 Aug;20(8):840-846. doi: 10.1038/gim.2017.190

Day(s) Performed

Monday through Sunday

Report Available

2 to 3 days

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 US Food and Drug Administration.

CPT Code Information

83789

LOINC Code Information

Test ID Test Order Name Order LOINC Value
PDBS Pompe Disease, BS 63416-2

 

Result ID Test Result Name Result LOINC Value
602290 Interpretation 59462-2
602300 Reviewed By 18771-6

Testing Algorithm

See Newborn Screen Follow-up for Pompe Disease in Special Instructions.

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

mml-biochemical