Test Code G6SW N-Acetylgalactosamine-6-Sulfatase, Leukocytes
Useful For
Preferred test to rule-out mucopolysaccharidosis IVA (Morquio A syndrome)
The test is not useful to establish carrier status for Morquio A syndrome.
Special Instructions
Reporting Name
N-Acetylgalactosamine 6 Slft, WBCSpecimen Type
Whole Blood ACDAdvisory Information
This test cannot be used to establish carrier status for Morquio A syndrome.
Shipping Instructions
For optimal isolation of leukocytes, it is recommended the specimen arrive within 7 days of collection to be stabilized. Collect specimen Monday through Thursday only and not the day before a holiday. Specimen should be collected and packaged as close to shipping time as possible.
Specimen Required
Container/Tube:
Preferred: Yellow top (ACD solution B)
Acceptable: Yellow top (ACD solution A)
Specimen Volume: 6 mL
Collection Instructions: Send specimen in original tube. Do not transfer blood to other containers.
Specimen Minimum Volume
5 mL
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Whole Blood ACD | Refrigerated (preferred) | 7 days | YELLOW TOP/ACD |
Ambient | 7 days | YELLOW TOP/ACD |
Reject Due To
Gross hemolysis | Reject |
Clinical Information
Mucopolysaccharidosis IVA, (MPS IVA; Morquio A syndrome) is an autosomal recessive mucopolysaccharidosis caused by reduced or absent N-acetylgalactosamine-6-sulfate sulfatase (GALNS) enzyme activity. The mucopolysaccharidoses are a group of disorders caused by the deficiency of any of the enzymes involved in the stepwise degradation of dermatan sulfate, heparan sulfate, keratan sulfate, or chondroitin sulfate (referred to as mucopolysaccharides: MPS or glycosaminoglycans: GAG). Accumulation of MPS in lysosomes interferes with normal functioning of cells, tissues, and organs.
Clinical features and severity of symptoms of MPS IVA are widely variable and affect multiple body systems. Clinical features may include skeletal dysplasia, short stature, dental anomalies, corneal clouding, respiratory insufficiency, and cardiac disease. Intelligence is usually normal. Treatment options are mostly limited to symptom management; however, more recently available enzyme replacement therapy has shown to be effective in improving some function and quality of life for individuals with MPS IVA. Estimates of the incidence of MPS IVA syndrome range from 1 in 200,000 to 1 in 300,000 live births.
A diagnostic workup in an individual with MPS IVA typically demonstrates elevated levels of urinary MPS and increased keratan sulfate and chondroitin-6-sulfate detected via quantitative and qualitative liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis of the specific sulfates. Morquio B is a distinct disorder caused by a deficiency of beta-galactosidase and has a significant number of overlapping clinical features with MPS IVA. Enzyme analysis is necessary to distinguish between the 2 types. Reduced or absent activity of N-acetylgalactosamine-6-sulfate sulfatase enzyme in leukocytes and/or fibroblasts can confirm a diagnosis of MPS IVA. Sequencing of the GALNS gene allows for detection of disease-causing variants in affected patients and identification of familial variants allows for testing of at-risk family members.
Reference Values
≥92 nmol/17 hour/mg protein
Day(s) and Time(s) Performed
Varies
Analytic Time
30 daysPerforming Laboratory

Test Classification
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
82657
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
G6SW | N-Acetylgalactosamine 6 Slft, WBC | 24096-0 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
62409 | N-Acetylgalactosamine 6 Slft, WBC | 24096-0 |
35778 | Interpretation (G6SW) | 59462-2 |
35777 | Reviewed By | 18771-6 |
NY State Approved
YesMethod Name
Fluorometric
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 in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Biochemical Genetics Patient Information (T602) in Special Instructions.
3. If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.
Testing Algorithm
See Lysosomal Storage Disorders Diagnostic Algorithm, Part 1 in Special Instructions.