Test ID: AGA
Alpha-Galactosidase, Leukocytes
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
Diagnosis of Fabry disease in males
Verifying abnormal serum alpha-galactosidase results in males with a clinical presentation suggestive of Fabry disease
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
Diagnosis of Fabry disease in males
Useful to verify abnormal serum alpha-galactosidase results in males with a clinical presentation suggestive of Fabry disease.
Enzyme testing is useful in identifying affected males. Enzyme levels for carriers are usually within the normal range. Order FABMS/88264 Fabry Disease, Full Gene Analysis for carrier testing
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
The following algorithms are available in Special Instructions:
-Fabry Disease: Newborn Screen-Positive Follow-up
-Fabry Disease Testing Algorithm
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
Fluorometric
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
Anderson Fabry Disease
Anderson-Fabry Disease
Ceramide Trihexosidase
Fabry Disease
Fabry's Disease
Galactosidase, Alpha
GLA Deficiency
Alpha-Gal A
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.
Specimen must arrive within 72 hours of draw to be stabilized. Specimen received after 72 hours could have falsely normal results. Draw specimen Monday through Thursday only and not the day before a holiday. Specimen should be drawn and packaged as close to shipping time as possible.
Container/Tube:
Preferred: Yellow top (ACD solution B)
Acceptable: Yellow top (ACD solution A)
Specimen Volume: 7 mL
Collection Instructions: Do not transfer blood to other containers.
Forms:
1. 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. 2. If not ordering electronically, submit a Biochemical Genetics Request Form (Supply T439) with the specimen.
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 | Mild OK; Gross reject |
| Lipemia | NA |
| Icterus | NA |
| Other | NA |
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 |
|---|---|---|
| Whole Blood ACD | Refrigerated (preferred) | 72 hours |
| Ambient | 72 hours |
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 glycosylsphingolipids in tissues throughout the body, in particular, the kidney, heart, and brain. More than 150 mutations in the GLA gene have been identified in individuals diagnosed with Fabry disease. Severity and onset of symptoms are dependent on the amount of residual enzyme activity. The classic form of Fabry disease occurs in males with less than 1% alpha-Gal A activity. Symptoms usually appear in childhood or adolescence and can include acroparesthesias (pain crises in the extremities), multiple angiokeratomas, reduced or absent sweating, and corneal opacity. In addition, progressive renal involvement leading to end-stage renal disease typically occurs in adulthood followed by cardiovascular and cerebrovascular disease. The estimated incidence is 1 in 40,000 males.
Males with residual alpha-Gal A activity may present with either a renal or cardiac form of Fabry disease with onset of symptoms later in life. Individuals with the renal variant typically present in the third decade with the development of renal insufficiency and, ultimately, end-stage renal disease. These individuals may or may not share other symptoms with the classic form of Fabry disease. Individuals with the cardiac variant are often asymptomatic until they present with cardiac findings such as cardiomyopathy, mitral insufficiency, or conduction abnormalities in the fourth decade. The cardiac variant is not associated with renal failure. Variant forms of Fabry disease may be underdiagnosed.
Females who are carriers of Fabry disease can have clinical presentations ranging from asymptomatic to severely affected and may have alpha-Gal A activity in the normal range; therefore, additional studies including molecular genetic analysis of the GLA gene (FABMS/88264 Fabry Disease, Full Gene Analysis) are recommended to detect carriers.
Reduced or absent alpha-Gal A in blood spots, leukocytes (AGA/8785 Alpha-Galactosidase, Leukocytes), or serum (AGAS/8784 Alpha-Galactosidase, Serum) can indicate a diagnosis of classic or variant Fabry disease. Molecular sequence analysis of the GLA gene (FABMS/88264 Fabry Disease, Full Gene Analysis) allows for detection of the disease-causing mutation in affected patients and carrier detection in females.
See Fabry Disease: Newborn Screen-Positive Follow-up algorithm and Fabry Disease Testing Algorithm in Special Instructions.
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.
> or =23.1 nmol/hour/mg protein
An interpretative report will be provided.
Note: Results from this assay do not reflect carrier status because of individual variation of alpha-galactosidase enzyme levels.
Interpretation Provides information to assist in interpretation of the test results
Deficiency of alpha-galactosidase A (alpha-Gal A) is diagnostic for Fabry disease in males.
Urine sediment analysis (CTSA/81979 Ceramide Trihexoside/Sulfatide Accumulation in Urine Sediment, Urine) for the accumulating trihexoside substrate is also recommended.
Carriers usually have alpha-galactosidase levels in the normal range.
See Fabry Disease: Newborn Screen-Positive Follow-up algorithm and Fabry Disease Testing Algorithm in Special Instructions.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Carrier detection using enzyme levels is unreliable; mutation analysis (FABMS/88264 Fabry Disease, Full Gene Analysis) is the recommended test.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Desnick RJ, Ioannou YA, Eng CM: a-Galactosidase A deficiency: Fabry disease. In The Metabolic Basis of Inherited Disease. Vol. 2. Seventh edition. Edited by CR Scriver, AL Beaudet, WS Sly, D Valle. New York, McGraw-Hill Book Company, 1995, pp 2741-2784
2. De Schoenmakere G, Poppe B, Wuyts B, et al: Two-tier approach for the detection of alpha-galactosidase A deficiency in kidney transplant recipients. Nephrol Dial Transplant 2008;23:4044-4048
3. Spada M, Pagliardini S, Yasuda M, et al: High incidence of later-onset Fabry disease revealed by newborn screening. Am J Hum Genet 2006;79:31-40
4. Mehta A, Hughes DA: Fabry Disease. GeneReviews. Edited by RA Pagon, TD Bird, CR Dolan, et al: University of Washington, Seattle. Last updated March 2011
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 Feb;81[2]:157-171)
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.
Specimens are processed Monday through Sunday. Assay is performed on Friday.
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.
82657
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 |
|---|---|---|
| 32302 | Reason for Referral | 42349-1 |
| 32303 | Method | 49549-9 |
| 8785 | Alpha-Galactosidase, Leukocytes | 24049-9 |
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