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25207 Alpha-Galactosidase, Serum (AGAS)

Alpha-Galactosidase, Serum (AGAS)
Test Code: AGASSO
Synonyms/Keywords
Alpha Galactosidase; Anderson Fabry Disease; Ceramide Trihexosidase; Fabry Disease; Fabry's Disease; Galactosidase, Alpha; GLA Deficiency;
Anderson-Fabry Disease
Useful For

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.

Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
Serum​ ​Serum Separator Tube (SST) Red Top Tube (RTT)
​2 mL ​0.2 mL
Collection Processing Instructions
Sex of patient is required for interpretation of results. 
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​Frozen (preferred) ​14 days
​Refrigerated ​24 hours
Interference

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

Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation
​Mayo Clinic Laboratories Tuesday, Friday
4 to 8 days
Fluorometric
Reference Lab
Test Information

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, 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.

 

​Genetics Test Information:

Serum is the preferred screening specimen for Fabry disease.

Enzyme testing is useful in identifying affected male patients.

 

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. Order FABRZ / Fabry Disease, Full Gene Analysis, Varies for testing carrier status.

Additional Testing Requirements:

Urine sediment analysis (CTSU / Ceramide Trihexosides and Sulfatides, Random, Urine) for the accumulating trihexoside substrate and measurement of globotriaosylsphingosine (LGB3S / Gobotriaosylsphingosine, Serum) are also recommended.

Reference Range Information
Performing Location Reference Range
​Mayo Clinic Laboratories

​0.074-0.457 U/L

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

Interpretation

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).

Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
82657​ ​1
Synonyms/Keywords
Alpha Galactosidase; Anderson Fabry Disease; Ceramide Trihexosidase; Fabry Disease; Fabry's Disease; Galactosidase, Alpha; GLA Deficiency;
Anderson-Fabry Disease
Ordering Applications
Ordering Application Description
​Centricity ​Alpha-Galactosidase, S (AGAS)
​Cerner ​None
If the ordering application you are looking for is not listed, contact your local laboratory for assistance.
Specimen Requirements
Specimen Type Preferred Container/Tube Acceptable Container/Tube Specimen Volume Specimen Minimum Volume
(allows for 1 repeat)
Pediatric Minimum Volume
(no repeat)
Serum​ ​Serum Separator Tube (SST) Red Top Tube (RTT)
​2 mL ​0.2 mL
Collection Processing
Sex of patient is required for interpretation of results. 
Specimen Stability Information
Specimen Type Temperature Time
​Serum ​ ​Frozen (preferred) ​14 days
​Refrigerated ​24 hours
Interference

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

Useful For

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.

Reference Range Information
Performing Location Reference Range
​Mayo Clinic Laboratories

​0.074-0.457 U/L

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

Interpretation

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).

For more information visit:
Performing Laboratory Information
Performing Location Day(s) Test Performed Report Available Methodology/Instrumentation
​Mayo Clinic Laboratories Tuesday, Friday
4 to 8 days
Fluorometric
Reference Lab
For billing questions, see Contacts
Outreach CPTs
CPT Modifier
(if needed)
Quantity Description Comments
82657​ ​1
For most current information refer to the Marshfield Laboratory online reference manual.