Test ID: AGABS
Alpha-Galactosidase, Blood Spot
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
Evaluation of patients with a clinical presentation suggestive of Fabry disease
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
See Fabry Disease Testing Algorithm in Special Instructions.
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 Enzyme Assay
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 Galactosidase
Anderson-Fabry Disease
Ceramide trihexosidase
Fabry Disease
Fabry's Disease
Galactosidase, Alpha
GLA Deficiency
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.
Container/Tube:
Preferred: Whatman Protein Saver 903 Paper
Acceptable: Ahlstrom 226 filter paper, Supplemental Newborn Screening Card (Supply T493)
Specimen Volume: 2 blood spots
Collection Instructions:
1. Do not use device or capillary tube containing EDTA to collect specimen.
2. An alternative blood collection option for a patient >1 year of age is fingerstick.
3. Let blood dry on the filter paper at ambient temperature in a horizontal position for 3 hours.
4. Do not expose specimen to heat or direct sunlight.
5. Do not stack wet specimens.
6. Keep specimen dry.
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 | NA |
| Lipemia | NA |
| Icterus | NA |
| Other | Blood spot specimen that shows serum rings or has multiple layers |
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 | Ambient (preferred) | 90 days |
| Frozen | 90 days | |
| Refrigerated | 90 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Fabry disease is an X-linked recessive lysosomal storage disorder resulting from deficient activity of the enzyme alpha-galactosidase A (a-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 <1% a-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 a-Gal A activity may present with either of 2 variant forms of Fabry disease (renal or cardiac) 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 a-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 a-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 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.
Males: > or =1.2 nmol/mL/h
Females: > or =2.8 nmol/mL/h
An interpretive report will be provided.
Interpretation Provides information to assist in interpretation of the test results
In male patients, results <1.2 nmol/mL/hour in properly submitted specimens are consistent with Fabry disease. Normal results (> or =1.2 nmol/mL/hour) are not consistent with Fabry disease.
In female patients, normal results (> or =2.8 nmol/mL/hour) in properly submitted specimens are typically not consistent with carrier status for Fabry disease; however, enzyme analysis, in general, is not sufficiently sensitive to detect all carriers. Because a carrier range has not been established in females, molecular genetic analysis of the GLA gene (FABMS/88264 Fabry Disease, Full Gene Analysis) should be considered when alpha-galactosidase A activity is <2.9 nmol/mL/hour, or if clinically indicated.
See 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
Specimens exposed to heat >25 degrees C for more than 48 hours will yield higher activity levels than properly submitted specimens. This may cause false-normal (false-negative) results in affected patients.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Chamoles NA, Blanco M, Gaggioli D: Fabry disease: enzymatic diagnosis in dried blood spots on filter paper. Clin Chim Acta 2001;308:195-196
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
Whole blood is collected on grade 903 (Whatman) filter paper. A one-eighth inch (3-mm) disk is punched out of the dried blood spot into a 96-well plate. 20 mcL of 0.25 M N-acetyl-D-galactosamine is added as elution liquid/inhibitor and 50 mcL of 5 mM 4-methylumbelliferyl-alpha-D-galactopyranoside in 0.15 M cit-phos buffer as the substrate (70 mcL total volume plus dried blood spot). After the incubation period (20 hours at 37 degrees C), all of the liquid from the plate is manually transferred to a second 96-well plate. 200 mcL of stop buffer (150 mM EDTA, pH 11.4) is added to all wells. A calibration is added to every plate and is derived from 4-methylumbelliferone (4-MU) that is serially diluted manually in the plate with the highest calibrator being equivalent to an enzyme activity of 12.2 nmol/mL/hr. The plate is then read on the spectrofluorometer. Fluorescence readings for duplicate wells are averaged and the average fluorescence is used to calculate the enzyme activity result. (Poeppl AG, Murray GJ, Medin JA: Enhanced filter paper enzyme assay for high-throughput population screening for Fabry disease. Anal Biochem 2005;337:161-163)
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.
Thursday; morning
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 |
|---|---|---|
| 50883 | Specimen | 31208-2 |
| 50884 | Specimen ID | N/A |
| 50885 | Source | N/A |
| 50886 | Order Date | N/A |
| 50887 | Reason For Referral | 42349-1 |
| 50888 | Method | In Process |
| 50889 | Alpha-Galactosidase, BS | 55908-8 |
| 50890 | Interpretation | 59462-2 |
| 50891 | Amendment | In Process |
| 50892 | Reviewed By | N/A |
| 50893 | Release Date | N/A |
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