Arylsulfatase A, Fibroblasts
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Detection of metachromatic leukodystrophy
Genetics Test Information Provides information that may help with selection of the correct test or proper submission of the test request
First order ARSAW/8779 Arylsulfatase A, Leukocytes and ARSU/8777 Arylsulfatase A, Urine.
Additional Tests Lists test(s) that are always performed, at an additional charge, with the initial test(s)
|Test ID||Reporting Name||Available Separately||Always Performed|
|CRYOB||Cryopreserve for Biochem Studies||No||Yes|
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
When this test is ordered, a fibroblast culture and cryopreservation for biochemical studies will always be performed at an additional charge. However, for multiple lysosomal enzyme assays on a patient utilizing fibroblast culture, only 1 culture is required regardless of the number of enzyme assays ordered. If viable cells are not obtained within 10 days, client will be notified.
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
ARST/8778: Colorimetric Enzyme Assay
FIBR/8482: Cultivated from Biopsy as Monolayer
CRYO/88832: Fibroblast Subculture Followed by Cryopreservation and Storage
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Arylsulfatase A, Fibroblasts
Arylsulfatase A deficiency
Arylsulfatase A 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.
This test is not recommended for prenatal testing.
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.
Submit only 1 of the following specimens:
Specimen Type: Cultured fibroblasts
Container/Tube: T-75 or T-25 flask
Specimen Volume: 1 full T-75 flask 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
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.
Specimen in formalin or fixative preservative
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by a deficiency of the arylsulfatase A enzyme, which leads to the accumulation of galactosyl sulfatide (cerebroside sulfate) in the white matter of the central nervous system and in the peripheral nervous system. Galactosyl sulfatide and, to a smaller extent, lactosyl sulfatide, also accumulate within the kidney, gallbladder, and other visceral organs, and are excreted in excessive amounts in the urine.
The 3 clinical forms of MLD are late-infantile, juvenile, and adult, depending on age of onset. All result in progressive neurologic changes and leukodystrophy demonstrated on magnetic resonance imaging. Late-infantile MLD is the most common (50%-60% of cases) and typically presents between 1 to 2 years of age with hypotonia, clumsiness, diminished reflexes, and slurred speech. Progressive neurodegeneration occurs with a typical disease course of 3 to 10 years. Juvenile MLD (20%-30% of cases) is characterized by onset between 4 to 14 years. Typical presenting features are behavior problems, declining school performance, clumsiness, and slurred speech. Neurodegeneration occurs at a somewhat slower and more variable rate than the late-infantile form. Adult MLD (15%-20% of cases) has an onset after puberty and can be as late as the fourth or fifth decade. Presenting features are often behavior and personality changes, including psychiatric symptoms; clumsiness, neurologic symptoms, and seizures are also common. The disease course has variable progression and may occur over 2 to 3 decades. The disease prevalence is estimated to be approximately 1 in 100,000.
MLD is an autosomal recessive disorder and is caused by mutations in the ARSA gene coding for the arylsulfatase A enzyme. This disorder is distinct from conditions caused by deficiencies of arylsulfatase B (Maroteaux-Lamy disease) and arylsulfatase C (steroid sulfatase deficiency).
Extremely low arylsulfatase A levels have been found in some clinically normal parents and other relatives of MLD patients. These individuals do not have metachromatic deposits in peripheral nerve tissues, and their urine content of sulfatide is normal. Individuals with this "pseudodeficiency" have been recognized with increasing frequency among patients with other apparently unrelated neurologic conditions as well as among the general population. This has been associated with a fairly common polymorphism in the arylsulfatase A gene, which leads to low expression of the enzyme (5%-20% of normal). These patients can be difficult to differentiate from actual MLD patients. Additional studies, such as molecular genetic testing of ARSA, urinary excretion of sulfatides (CTSA/81979 Ceramide Trihexoside/Sulfatide Accumulation in Urine Sediment, Urine) and/or histological analysis for metachromatic lipid deposits in nervous system tissue are recommended to confirm a diagnosis.
Current treatment options for MLD are usually focused on managing disease manifestations such as seizures. Bone marrow transplantation remains controversial, and the effectiveness of enzyme replacement therapy may be limited due to difficulties crossing the blood-brain barrier. Other treatments under ongoing investigation include hematopoietic stem cell transplantation and fetal umbilical cord blood transplantation.
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.
2.28-15.74 U/g of cellular protein
In metachromatic leukodystrophy (MLD), the activity of serum arylsulfatase A is greatly reduced. Values expected in MLD are <1.5 U/g of cellular protein.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test is not suitable for carrier status detection due to both analytical and unusual genetic variation.
Depression of arylsulfatase activity does not clearly indicate metachromatic leukodystrophy. The pseudogene could be present resulting in lowered activity. Arylsulfatase A is also deficient in individuals with multiple sulfatase deficiency.
Interfering factors include lack of viable cells, bacterial contamination, failure to transport tissue in an appropriate media, excessive transport time, and exposure of the specimen to temperature extremes (freezing or >30 degrees C).
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Jaeken J, Gieselmann V, von Figura K: Metachromatic leukodystrophy. In Scriver's The Online Metabolic and Molecular Basis of Inherited Disease (OMMBID). Edited by D Valle, et al, The McGraw-Hill Companies, Inc. Available from URL: ttp://www.ommbid.com/OMMBID/a/c.html/lysosomal_disorders/metachromatic_leukodystrophy/abstract
2. Fluharty AL: Arylsulfatase A Deficiency. Available from URL: http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=krabbe Reviewed September 23, 2008
Method Description Describes how the test is performed and provides a method-specific reference
The enzymatic diagnosis of metachromatic leukodystrophy depends on measurement of the rate of release of sulfate from p-nitrocatechol sulfate. As sulfate is released, the liberated p-nitrocatechol is measured in alkaline solution at 515 nm.(Austin JH, Balasubramanian AS, Pittabiraman TN, et al: A controlled study of enzymic activities in three human disorders of glycolipid metabolism. J Neurochem 1963;10:805-816)
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.
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.
30-45 days depending on rapidity of growth
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
3 years - Check with the lab for availability.
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.
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. 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 Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
88240-Cryopreservation for biochemical studies
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|
|8778||Arylsulfatase A, Fibroblasts||24077-0|