Test Code ARSAB Arylsulfatase A, Blood Spot
Ordering Guidance
This test primarily serves as a second-tier assay to be used by newborn screening programs to screen for metachromatic leukodystrophy when first tier sulfatide analysis is abnormal. The test can also be used to screen patients at risk for metachromatic leukodystrophy.
Specimen Required
Supplies: Card-Blood Spot Collection (Filter Paper) (T493)
Container/Tube:
Preferred: Card-Blood Spot Collection (Filter Paper)
Acceptable: PerkinElmer 226 filter paper, Munktell filter paper, Whatman protein Saver 903 paper, local newborn screening card, or blood collected in tubes containing EDTA (preferred) or heparin and dried on filter paper
Specimen Volume: 2 Blood spots
Collection Instructions:
1. Completely fill at least 2 circles on the filter paper card (approximately 100 microliters blood per circle).
2. Let blood dry on filter paper at ambient temperature in a horizontal position for a minimum of 3 hours.
3. Do not expose specimen to heat or direct sunlight.
4. Do not stack wet specimens.
5. Keep specimen dry and freeze (with desiccant if necessary).
Additional Information:
1. For collection instructions, see Blood Spot Collection Instructions
2. For collection instructions in Spanish, see Blood Spot Collection Card-Spanish Instructions (T777)
3. For collection instructions in Chinese, see Blood Spot Collection Card-Chinese Instructions (T800)
Genetics Test Information
Metachromatic leukodystrophy is caused by deficient activity of arylsulfatase A (ARSA) enzyme and is characterized by progressive neurologic changes and leukodystrophy with variable age of onset.
Pseudodeficiency of ARSA enzyme has been recognized among patients with other unrelated neurologic conditions as well as among the general population.
Additional studies, such as molecular genetic testing of ARSA (CGPH / Custom Gene Panel, Hereditary, Next-Generation Sequencing, Varies; specify ARSA Gene List ID: IEMCP-WHFH2K), urinary excretion of sulfatides (CTSU / Ceramide Trihexosides and Sulfatides, Random, Urine), and, if necessary, histological analysis for metachromatic lipid deposits in nervous system tissue are recommended to confirm a diagnosis.
Specimen Type
Whole bloodSpecimen Minimum Volume
1 Blood spot
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Whole blood | Frozen (preferred) | 28 days | FILTER PAPER |
Refrigerated | 14 days | FILTER PAPER |
Reject Due To
Blood spot specimen that shows serum rings or has multiple layers | Reject |
Nonapproved filter paper | Reject |
Reference Values
Normal: ≥0.100 mmol/mL/hr
Day(s) Performed
Monday, Thursday
Report Available
3 to 6 daysSpecimen Retention Time
6 monthsPerforming Laboratory

CPT Code Information
82657