Test Catalog

Test Id : AGAS

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Alpha-Galactosidase, Serum

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Overview

Test Catalog

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

Diagnosis of Fabry disease in male patients

 

Preferred screening test (serum) for Fabry disease

 

This test is not useful for patients undergoing a work up for a meat or meat-derived product allergy.

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Serum is the preferred screening specimen for Fabry disease.

 

Enzyme testing is useful in identifying affected male patients.

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

The following algorithms are available:

-Fabry Disease: Newborn Screen-Positive Follow-up

-Fabry Disease Diagnostic Testing Algorithm

 

If the patient has abnormal newborn screening results for Fabry disease, refer to the appropriate ACMG Newborn Screening ACT Sheet.(1)

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

Fluorometric

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

Alpha-Galactosidase, S

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

Alpha Galactosidase

Anderson Fabry Disease

Ceramide Trihexosidase

Fabry Disease

Fabry's Disease

Galactosidase, Alpha

GLA Deficiency

Anderson-Fabry Disease

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

The following algorithms are available:

-Fabry Disease: Newborn Screen-Positive Follow-up

-Fabry Disease Diagnostic Testing Algorithm

 

If the patient has abnormal newborn screening results for Fabry disease, refer to the appropriate ACMG Newborn Screening ACT Sheet.(1)

Specimen Type
Describes the specimen type validated for testing

Serum

Ordering Guidance

If testing needed for assessment of meat or meat-derived product allergy, order either ALGAL / Galactose-Alpha-1,3-Galactose (Alpha-Gal), IgE, Serum or APGAL / Galactose-Alpha-1,3-Galactose (Alpha-Gal) Mammalian Meat Allergy Profile, Serum.

 

Carrier detection using enzyme levels is unreliable for female patients as results may be within the normal values. For testing carrier status, order FABRZ / Fabry Disease, Full Gene Analysis, Varies.

Additional Testing Requirements

Urine sediment analysis for the accumulating trihexoside substrate and measurement of globotriaosylsphingosine are recommended. Order both CTSU / Ceramide Trihexosides and Sulfatides, Random, Urine and LGB3S / Globotriaosylsphingosine, Serum.

Necessary Information

Sex of patient is required for interpretation of results.

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

Collection Container/Tube:

Preferred: Serum gel

Acceptable: Red top

Submission Container/Tube: Plastic vial

Specimen Volume: 2 mL

Collection Instructions: Centrifuge and aliquot serum into a plastic vial.

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:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

2. Biochemical Genetics Patient Information (T602)

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. The minimum volume is sufficient for one attempt at testing.

0.3 mL

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

  All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

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
Serum Frozen (preferred) 14 days
Refrigerated 24 hours

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

Diagnosis of Fabry disease in male patients

 

Preferred screening test (serum) for Fabry disease

 

This test is not useful for patients undergoing a work up for a meat or meat-derived product allergy.

Genetics Test Information
Provides information that may help with selection of the correct genetic test or proper submission of the test request

Serum is the preferred screening specimen for Fabry disease.

 

Enzyme testing is useful in identifying affected male patients.

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

The following algorithms are available:

-Fabry Disease: Newborn Screen-Positive Follow-up

-Fabry Disease Diagnostic Testing Algorithm

 

If the patient has abnormal newborn screening results for Fabry disease, refer to the appropriate ACMG Newborn Screening ACT Sheet.(1)

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

Fabry disease is an X-linked lysosomal storage disorder resulting from deficient activity of the enzyme alpha-galactosidase A (alpha-Gal A) and the subsequent deposition of glycosphingolipids in tissues throughout the body; in particular, in the kidney, heart, and brain. Variants within the GLA gene cause Fabry disease and more than 630 variants have been identified. Severity and onset of symptoms are dependent on the amount of residual enzyme activity. The classic form of Fabry disease occurs in male patients who have less than 1% alpha-Gal A activity. Symptoms usually appear in childhood or adolescence and can include acroparesthesias (burning pain in the extremities), gastrointestinal issues, multiple angiokeratomas, reduced or absent sweating, corneal opacity, and proteinuria. In addition, progressive renal involvement leading to kidney failure, also called end-stage renal (kidney) disease (ESRD), typically occurs in adulthood, followed by cardiovascular and cerebrovascular disease. The estimated incidence varies from 1 in 3000 infants detected via newborn screening to 1 in 10,000 males diagnosed after onset of symptoms.

 

Male patients with residual alpha-Gal A activity greater than 1% may present with 1 of 3 variant forms of Fabry disease with onset of symptoms later in life: a renal variant associated with ESRD but without the pain or skin lesions; a cardiac variant typically presenting in the sixth to eighth decade with left ventricular hypertrophy, cardiomyopathy and arrhythmia, and proteinuria, but without ESRD; and a cerebrovascular variant presenting as stroke or transient ischemic attack. The variant forms of Fabry disease may be underdiagnosed.

 

Female patients who are carriers of Fabry disease can have clinical presentations ranging from asymptomatic to severely affected. Measurement of alpha-Gal A activity is not generally useful for identifying carriers of Fabry disease, as many of these individuals have normal levels of alpha-Gal A. Therefore, molecular genetic analysis of the GLA gene (FABRZ / Fabry Disease, Full Gene Analysis, Varies) is recommended to detect carriers.

 

Unless irreversible damage has already occurred, treatment with enzyme replacement therapy has led to significant clinical improvement in affected individuals. In addition, some (adult) patients may be candidates for oral chaperone therapy. For this reason, early diagnosis and treatment are desirable, and in a few US states, early detection of Fabry disease through newborn screening has been implemented.

 

Absent or reduced alpha-Gal A in blood spots (AGABS / Alpha-Galactosidase, Blood Spot), leukocytes (AGAW / Alpha-Galactosidase, Leukocytes), or serum (AGAS / Alpha-Galactosidase, Serum) can indicate a diagnosis of classic or variant Fabry disease. Molecular sequence analysis of the GLA gene (FABRZ / Fabry Disease, Full Gene Analysis, Varies) allows for detection of the disease-causing variant in both male and female patients. The biomarkers globotriaosylsphingosine (LGB3S / Globotriosylsphingosine, Serum) and ceremide trihexosides (CTSU / Ceramide Trihexosides and Sulfatides, Random, Urine) are typically elevated in symptomatic patients with Fabry disease and may aid in the diagnostic evaluation of female patients and individuals with a variant of uncertain significance in GLA.

 

See Fabry Disease Testing Algorithm and Fabry Disease: Newborn Screen-Positive Follow-up

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.

0.074-0.457 U/L

 

Note: Results from this assay are not useful for female carrier determination. Carriers usually have levels in the normal range.

Interpretation
Provides information to assist in interpretation of the test results

Deficiency (<0.016 U/L) of alpha-galactosidase in properly submitted specimens is diagnostic for Fabry disease in male patients. If concerned about specimen integrity, recheck using leukocyte testing (AGAW / Alpha-Galactosidase, Leukocytes).

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

Individuals with pseudodeficiency allelic variants can show reduced alpha-galactosidase A enzyme activity with this assay.

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

1. ACMG Newborn Screening ACT Sheets. Accessed October 30, 2023. Available at www.acmg.net/ACMG/Medical-Genetics-Practice-Resources/ACT_Sheets_and_Algorithms/ACMG/Medical-Genetics-Practice-Resources/ACT_Sheets_and_Algorithms.aspx?hkey=9d6bce5a-182e-42a6-84a5-b2d88240c508

2. Desnick RJ, Ioannou YA, Eng CM: Alpha-galactosidase A deficiency: Fabry disease. In: Valle D, Antonarakis S, Ballabio A, Beaudet AL, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease. McGraw-Hill; 2019. Accessed October 30, 2023. Available at https://ommbid.mhmedical.com/content.aspx?sectionid=225546984

3. Mehta A, Hughes DA. Fabry Disease. In: Adam MP, Feldman J, Mirzaa GM, et al., eds. GeneReviews. Seattle (WA): University of Washington, Seattle; August 5, 2002

4. Laney DA, Bennett RL, Clarke V, et al. Fabry disease practice guidelines: Recommendations of the National Society of Genetic Counselors. J Genet Couns. 2013;22(5):555-564. doi: 10.1007/s10897-013-9613-3

5. Laney DA, Peck DS, Atherton AM, et al. Fabry disease in infancy and early childhood: a systematic literature review. Genet Med. 2015;17(5)323-330. doi: 10.1038/gim.2014.120

6. Ferreira S, Auray-Blais C, Boutin M, et al. Variations in the GLA gene correlate with globotriaosylceramide and globotriaosylsphingosine analog levels in urine and plasma. Clin Chim Acta. 2015;447:96-104. doi: 10.1016/j.cca.2015.06.003

7. Nowak A, Beuschlein F, Sivasubramaniam V, Kasper D, Warnock DG. Lyso-Gb3 associates with adverse long-term outcome in patients with Fabry disease. J Med Genet. 2022;59(3):287-293. doi: 10.1136/jmedgenet-2020-107338

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

Alpha-galactosidase is a lysosomal enzyme active at an acidic pH. The enzyme hydrolyzes artificial substrates such as 4-methylumbelliferyl and alpha-D galactopyranoside. The 4-methylumbelliferone liberated is measured by fluorometry.(Desnick RJ, Allen KY, Desnick SJ, et al: Fabry's disease: enzymatic diagnosis of hemizygotes and heterozygotes. Alpha-galactosidase activities in plasma, serum, urine, and leukocytes. J Lab Clin Med. 1973;81[2]:157-171; Cowan T, Pasquali M. Laboratory investigations of inborn errors of metabolism. In: Sarafoglou K, Hoffman GF, Roth KS, eds. Pediatric Endocrinology and Inborn Errors of Metabolism. 2nd ed. McGraw-Hill; 2017:1139-1158)

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.

Tuesday, Friday

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 5 days

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

1 month

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 account representative. 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. It 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.

82657

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
AGAS Alpha-Galactosidase, S 1813-5
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.
50590 Alpha-Galactosidase,S 1813-5
50584 Interpretation 59462-2
50586 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 | 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

Test Update Resources

Change Type Effective Date
File Definition - Result ID 2024-01-18