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Test ID G6ST N-Acetylgalactosamine-6-Sulfate Sulfatase, Fibroblasts

Useful For

Assisting in the diagnosis of Morquio A syndrome in fibroblast specimens


The test is not useful to establish carrier status for Morquio A syndrome.

Genetics Test Information

Not recommended for carrier detection.


Morquio A is an autosomal recessive mucopolysaccharidosis caused by reduced or absent N-acetylgalactosamine-6-sulfate sulfatase (GALNS) enzyme activity.


Although clinically similar, Morquio A is genetically and enzymatically distinct from Morquio B. Enzyme analysis is necessary to distinguish between the 2.

Method Name

G6ST: Fluorometric

FIBR: Cultivated from Biopsy as Monolayer

CRYOB: Fibroblast Subculture Followed by Cryopreservation and Storage

Reporting Name

N-Acetylgalactosamine 6 Slft, Fibro

Specimen Type


Advisory Information

This test is not recommended for prenatal testing.


The preferred test to rule-out mucopolysaccharidosis IVA (Morquio A syndrome) is G6SW / N-Acetylgalactosamine-6-Sulfatase, Leukocytes.

Specimen Required

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

Supplies: Fibroblast Biopsy Transport Media (T115)

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 [T115]).

Specimen Volume: 4-mm punch

Specimen Stability Information: Refrigerated (preferred)/Ambient

Specimen Minimum Volume

See Specimen Required

Specimen Stability Information

Specimen Type Temperature Time
Tissue Varies

Reference Values

≥163 nmol/17 hour/mg protein

Day(s) and Time(s) Performed


Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

82657-N-Acetylgalactosamine-6-sulfate sulfatase

88233-Fibroblast culture

88240-Cryopreservation for biochemical studies

LOINC Code Information

Test ID Test Order Name Order LOINC Value
G6ST N-Acetylgalactosamine 6 Slft, Fibro 24095-2


Result ID Test Result Name Result LOINC Value
35766 N-Acetylgalactosamine 6 Slft, Fibro 24095-2
29726 Interpretation (G6ST) 59462-2
29728 Reviewed By 18771-6

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.

Testing Algorithm

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.

Additional Tests

Test ID Reporting Name Available Separately Always Performed
FIBR Fibroblast Culture Yes Yes
CRYOB Cryopreserve for Biochem Studies No Yes


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.