Test ID: GAAMS
Pompe Disease, Full Gene Sequencing
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Confirmation of diagnosis of Pompe disease (as a follow up to biochemical analyses)
Reflex Tests Lists test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| FBC | Fibroblast Culture for Genetic Test | Yes | No |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
If skin biopsy is received, fibroblast culture for genetic test will be added and charged separately.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
GAAMS/89898: Polymerase Chain Reaction (PCR) Followed by DNA Sequence Analysis
(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)
FBC/80333: Cell Culture
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Alpha Glucosidase
GAA Gene
Glycogen Storage Disease Type II (GSD II)
GSD II (Glycogen Storage Disease Type II)
Pompe Disease
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
Forms:
1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.
2. Molecular Genetics-Biochemical Disorders Patient Information Sheet (Supply T527) in Special Instructions
3. If not ordering electronically, submit a Molecular Genetics Request Form (Supply T245) with the specimen.
Specimen must arrive within 96 hours of collection.
Submit only 1 of the following specimens:
Preferred:
Specimen Type: Blood
Container/Tube:
Preferred: Lavender top (EDTA) or yellow top (ACD)
Acceptable: Any anticoagulant
Specimen Volume: 3 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send specimen in original tube.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Specimen Type: Cultured fibroblasts
Container/Tube: T-75 or T-25 flask
Specimen Volume: 1 full T-75 or 2 full T-25 flasks
Specimen Stability Information: Ambient (preferred)/Refrigerated 24 hours
Specimen Type: Skin biopsy
Container/Tube: Sterile container with any standard cell culture media (eg, minimal essential media, RPMI 1640). The solution should be supplemented with 1% penicillin and streptomycin. Tubes can be supplied upon request (Eagle's minimum essential medium with 1% penicillin and streptomycin [Supply T115]).
Specimen Volume: 4-mm punch
Specimen Stability Information: Refrigerated (preferred)/Ambient
Acceptable:
Specimen Type: Blood spot
Container/Tube: Whatman Protein Saver 903 Paper
Specimen Volume: 5 blood spots
Collection Instructions:
1. Let blood dry on the filter paper at ambient temperature in a horizontal position for 3 hours.
2. Do not expose specimen to heat or direct sunlight.
3. Do not stack wet specimens.
4. Keep specimen dry.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | Formalin or fixative |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Varies | Varies | |
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 condition caused by deficiency of acid alpha-glucosidase. Enzyme insufficiency results in symptoms such as muscle weakness, cardiomyopathy, and respiratory problems. Mutations in the GAA gene (which encodes acid alpha-glucosidase) are associated with Pompe disease.
The diagnosis of this heterogeneous condition relies on both clinical and laboratory evaluation. Clinically, the condition is categorized into infantile and late-onset forms based on age of onset, organ involvement, and rate of progression. The infantile form (or classic Pompe disease) is the most severe form and is characterized by early onset and rapid progression of cardiac, liver, and muscle problems resulting in death within the first year. The infantile variant form has a similar age of onset but a milder clinical presentation. On the less severe end of the spectrum is the late-onset form with childhood, juvenile, or adult onset. The rate of progression and severity of symptoms is quite variable, particularly in the late-onset forms. The incidence varies by clinical type and ethnic population; the combined incidence is approximately 1 in 40,000 individuals.
Biochemical testing of acid alpha-glucosidase in blood spot specimens or fibroblasts is useful for individuals with a suspected diagnosis of Pompe disease (GAABS/89210 Acid Alpha-Glucosidase, Blood Spot). When clinical manifestations and results of that analysis are supportive of a diagnosis of Pompe disease, mutation analysis of the GAA gene is warranted.
Over 250 different mutations have been identified in this gene including point mutations and large deletions. GAA full gene sequencing provided by this test will detect 2 mutations in approximately 83% to 93% of individuals with confirmed GAA enzyme deficiency. Identification of mutations provides confirmation of the diagnosis and allows for subsequent testing of at risk family members.
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.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
A small percentage of individuals who are carriers or have a diagnosis of Pompe disease may have a mutation that is not identified by this method (eg, large genomic deletions or duplications, promoter mutations). The absence of a mutation(s), therefore, does not eliminate the possibility of positive carrier status or the diagnosis of Pompe disease. For carrier testing, it is important to first document the presence of a GAA gene mutation in an affected family member.
In some cases, DNA alterations of undetermined significance may be identified.
Rare polymorphisms exist that could lead to false-negative or false-positive results. If results obtained do not match the clinical findings, additional testing should be considered.
A previous bone marrow transplant from an allogenic donor will interfere with testing. Call Mayo Medical Laboratories for instructions for testing patients who have received a bone marrow transplant.
Test results should be interpreted in the context of clinical findings, family history, and other laboratory data. Errors in our interpretation of results may occur if information given is inaccurate or incomplete.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Kishnani PS, Steiner RD, Bali D, et al: Pompe disease diagnosis and management guideline. Genet Med 2006 May;8(5):267-288
2. Van der Ploeg AT, Reuser AJJ: Pompe’s disease. Lancet 2008;372(9646):1342-1353
3. Kroos M, Pomponio RJ, van Vliet L, et al: Update of the Pompe disease mutation database with 107 sequence variants and a format for severity rating. Hum Mut 2008;29(6):E13-26
4. Hirschhorn R, Reuser AJJ. Glycogen storage disease type II: (acid maltase) deficiency. In Online Metabolic and Molecular Bases of Inherited Disease (OMMBID). Edited by CR Scriver, AL Beaudet, WS Sly, et al: New York, McGraw-Hill, Inc., available at www.ommbid.com Accessed 3-6-08
Method Description Describes how the test is performed and provides a method-specific reference
Fluorescent DNA sequence analysis is used to test for the presence of mutations in all 19 coding exons of the GAA gene. GenBank accession number; NM_ 000152.3. (Unpublished Mayo method)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Wednesday; 10 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
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's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
81406-GAA (glucosidase, alpha; acid) (eg, glycogen storage disease type II [Pompe disease]), full gene sequence
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| 50967 | Specimen | 31208-2 |
| 50968 | Specimen ID | N/A |
| 50969 | Source | N/A |
| 50970 | Order Date | N/A |
| 50971 | Reason For Referral | 42349-1 |
| 50972 | Method | In Process |
| 50973 | Result | In Process |
| 50974 | Interpretation | 69047-9 |
| 50975 | Extraction Performed? | N/A |
| 50976 | Amendment | In Process |
| 50977 | Reviewed By | N/A |
| 50978 | Release Date | N/A |
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