Test Catalog

Test Id : PD2T

Pompe Disease Second-Tier Newborn Screening, Blood Spot

Useful For
Suggests clinical disorders or settings where the test may be helpful

Second-tier testing of newborns with an abnormal primary screening result for Pompe disease (decreased acid alpha-glucosidase enzyme activity)

 

Follow-up testing for evaluation of an abnormal newborn screening result for Pompe disease

Highlights

This test is used as a second-tier newborn screen for Pompe disease and is based upon a ratio calculated between the creatine and creatinine ratio and the activity of acid-alpha glucosidase (GAA).

 

This test can help differentiate true cases of infantile and late onset Pompe disease from false-positive cases (such as carriers and pseudodeficiency of GAA enzyme).

 

A positive test result supports the utility of follow-up molecular genetic analysis of the GAA gene.

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

 

For more information, see Newborn Screening Act Sheet Pompe Disease: Decreased Acid Alpha-Glucosidase in Special Instructions.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

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

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

Pompe Disease 2ND Tier NBS, BS

Aliases
Lists additional common names for a test, as an aid in searching

Pompe disease

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

 

For more information, see Newborn Screening Act Sheet Pompe Disease: Decreased Acid Alpha-Glucosidase in Special Instructions.

Specimen Type
Describes the specimen type validated for testing

Whole blood

Ordering Guidance

Due to reference range differences, this test is the appropriate test for patients less than or equal to 6 weeks of age. For patients greater than 6 weeks of age, order PDBS / Pompe Disease, Blood Spot.

Necessary Information

1. Birth weight (grams)

2. Time of birth (24-hour time)

3. Gestational age (weeks)

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

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 then spotted and dried on filter paper.

Specimen Volume: 3 blood spots

Collection Instructions:

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

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

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

4. Do not stack wet specimens.

5. 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.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

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.

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

1 Blood spot

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Shows serum rings
Insufficient specimen
Layering
Multiple applications
Incubated/exposed to temperatures above 37 degrees C
Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

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

Useful For
Suggests clinical disorders or settings where the test may be helpful

Second-tier testing of newborns with an abnormal primary screening result for Pompe disease (decreased acid alpha-glucosidase enzyme activity)

 

Follow-up testing for evaluation of an abnormal newborn screening result for Pompe disease

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

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

 

For more information, see Newborn Screening Act Sheet Pompe Disease: Decreased Acid Alpha-Glucosidase in Special Instructions.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

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.

 

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 early diagnosis of Pompe disease desirable, as early initiation of treatment may improve prognosis. Newborn screening can identify patients with all forms of Pompe disease, even before onset of symptoms. Unaffected patients with GAA pseudodeficiency alleles and carriers may also be identified by newborn screening.

 

The ratio, calculated using the creatine:creatinine 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). When applied to the newborn screening setting, this second-tier testing can provide results 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
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

An interpretive report will be provided.

Interpretation
Provides information to assist in interpretation of the test results

An interpretive report will be 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 within Mayo Clinic Laboratories. Recommendations for additional biochemical testing and confirmatory studies (enzyme assay, molecular analysis) are provided in the interpretative report.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test may not detect some milder or later onset forms of Pompe disease.

 

Carrier status (heterozygosity) for Pompe disease cannot be reliably detected.

 

A positive test result is strongly suggestive of a diagnosis but requires follow-up using a stand-alone biochemical or molecular assay, which is best coordinated by local genetics providers.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Pascual JM, Roe CR: Systemic metabolic abnormalities in adult-onset acid maltase deficiency: beyond muscle glycogen accumulation. 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

3. Minter Baerg MM, Stoway SD, Hart J, et al: Precision newborn screening for lysosomal disorders. Genet Med. 2018 Aug;20(8):847-854. doi: 10.1038/gim.2017.194

4. Ames EG, Fisher R, Kleyn M, Ahmad A: Current Practices for U.S. Newborn Screening of Pompe Disease and MPSI. Int J Neonatal Screen. 2020 Sep 2;6(3):72. doi: 10.3390/ijns6030072

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Description
Describes how the test is performed and provides a method-specific reference

Dried blood spots are processed using 2 analytical protocols with postanalytical integration of all test results.

 

Protocol 1:

A dried blood spot is extracted by the addition of methanol with known concentrations of isotopically labeled amino acids and acylcarnitines, which are used as internal standards. The extract is derivatized by the addition of 3M HCl in n-butanol. From the residual blood spot a second extraction and derivatization is performed and analyzed concurrently by flow injection tandem mass spectrometry for creatine and creatinine.(Turgeon C, Magera M, Allard P, et al: Combined newborns screening for succinylacetone, amino acids, and acylcarnitines in dried blood spots. Clin Chem. 2008 Apr;54[4]:657-664)

 

Protocol 2:

Two 3-mm dried blood spots are excised from a single specimen and placed into individual plates. One spot is treated with a solution containing substrate and internal standard for acid sphingomyelinase, beta-glucocerebrosidase, alpha-glucosidase, alpha-galactosidase, galactocerebrosidase, and alpha-L-iduronidase. The enzyme plate is sealed and incubated overnight. Following the incubation the enzyme plate is purified by liquid-liquid extraction. The second dried blood spot is extracted with methanol containing d4-C26 lysophosphatidylcholines (LPC) on day 2 of the procedure. The LPC extracts and enzyme products are combined and analyzed concurrently flow injection tandem mass spectrometry.(Tortorelli S, Turgeon CT, Gavrilov DK, et al: Simultaneous testing for 6 lysosomal storage disorders and X-adrenoleukodystrophy in dried blood spots by tandem mass spectrometry. Clin Chem. 2016 Sep;62[9]:1248-1254)

PDF Report
Indicates whether the report includes an additional document with charts, images or other enriched information

No

Day(s) Performed
Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Sunday

Report Available
The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 3 days

Specimen Retention Time
Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

6 months

Performing Laboratory Location
Indicates the location of the laboratory that performs the test

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

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
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

83789

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
PD2T Pompe Disease 2ND Tier NBS, BS 63416-2
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
BG700 Birth Weight (grams, XXXX) 8339-4
BG701 Time of Birth (24hr time, XX:XX) 57715-5
BG702 Gestational Age (weeks, XX.X) 76516-4
48436 Interpretation 63416-2
48435 Reviewed By 18771-6

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Create a PDF

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports