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Lab Dept:


Test Name:


General Information

Lab Order Codes:



Metachromic Leukodystrophy; Mucolipidoses, Types II and III; ARS-A (Arylsulfatase A); WBC Aryl Sulfatase A

CPT Codes:

82657 – Enzyme activity in blood cells, cultured cells, or tissue, not elsewhere specified; nonradioactive substrate

Test Includes:

Arylsulfatase A, Leukocyte level reported in nmol/h/mg.


Test Indications:

Leukocyte assay is the preferred test to order first to rule out metachromatic leukodystrophy. Not reliable in identifying carriers due both to analytical variation and unusual genetic variants. The urine assay should be used in confirming leukocyte results.

Lab Testing Sections:

Chemistry - Sendouts

Referred to:

Mayo Medical Laboratories (MML Test: 8779/ARSAW)

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Daily, 24 hours (Specimen must be received by reference lab within 48 hours of collection and must be received 1 day prior to assay day for processing)

Turnaround Time:

4 – 8 days; test set up Monday, Thursday

Special Instructions:

Specimen must arrive within 48 hours of draw. Obtain special collection tube from the laboratory.


Specimen Type:

Whole blood


Yellow top (ACD Solution A or B) tube available from laboratory

Draw Volume:

7 mL (Minimum: 5 mL) ACD Whole blood

Processed Volume:

Same as Draw Volume


Routine venipuncture

Special Processing:

Lab Staff: Do Not process specimen, leave in original draw container. Refrigerate specimen. Do Not transfer blood to other containers. Forward promptly at refrigerated temperatures.

Patient Preparation:


Sample Rejection:

Frozen or warm specimens; specimens other than ACD; gross hemolysis; mislabeled or unlabeled specimens


Reference Range:

> or = 62 nmol/h/mg

Interpretation: Detection of metachromatic leukodystrophy (MLD)

Note: Results from this assay do not reflect carrier status because of individual variation of arylsulfatase A enzyme levels. Low normal values may be due to the presence of pseudodeficiency gene or carrier gene. Patients with these depressed levels may be phenotypically normal.

Critical Values:



This test may not be reliable in identifying carriers due botht o analytical variation and unusual genetic variants.


Colorimetric Enzyme Assay


Mayo Medical Laboratories (February 2011)


2/15/2011: Change in reporting units. Previously reported as U/1010 cells.

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