Hexosaminidase A and Total, Leukocytes/Molecular Reflex, Whole Blood
Use
This test is essential for the carrier detection and diagnosis of Tay-Sachs disease and Sandhoff disease. Both are lysosomal storage disorders caused by deficiencies of hexosaminidase A and B enzymes, leading to the accumulation of GM2 ganglioside and clinical symptoms. This test measures enzyme activity levels, indicates the necessity of reflex testing with next-generation sequencing for HEXA or HEXB genes, and differentiates between possible carrier, affected, and non-disease-causing pseudodeficiency alleles. Enzyme analysis helps distinguish between Tay-Sachs and Sandhoff diseases.
Special Instructions
Collect specimen Monday through Thursday and not the day before a holiday for optimal leukocyte isolation. Use yellow top (ACD solution B) tubes, and do not aliquot. The specimen should be collected and shipped as close to collection time as possible, refrigerated, and arrive within 6 days. Forms require New York client informed consent documented. For assistance or fee inquiries, contact Mayo Clinic Laboratories. Molecular reflex testing performed as needed depending on initial results.
Limitations
A small percentage of carriers with normal hexosaminidase A activity may not be detected by this test. GM2 activator deficiency, a rare disorder with clinical features similar to Tay-Sachs and Sandhoff diseases, cannot be detected with this assay. Regions in genes with homology, high GC content, or repetitive sequences may not be effectively evaluated. Variant confirmation may require alternate methodologies as determined by internal criteria.
New York Approved
Methodology
Other
Biomarkers
LOINC Codes
- 87543-5
- 24075-4
- 23825-3
- 59462-2
- 18771-6
Result Turnaround Time
2-8 days
Related Documents
For more information, please review the documents below
Specimen
Whole Blood
Volume
6 mL
Minimum Volume
5 mL
Container
Yellow top (ACD solution B preferred, solution A acceptable)
Collection Instructions
Send whole blood specimen in original tube. Do not aliquot.
Storage Instructions
Refrigerate within 6 days of collection to stabilize leukocytes.
Causes for Rejection
Gross hemolysis
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 6 days |
| Refrigerated | 6 days |