Hexosaminidase A, Serum
Use
The Hexosaminidase A, Serum test is primarily used as a second-order diagnostic tool for determining the presence of the B1 variant of Tay-Sachs disease. Tay-Sachs is a lysosomal storage disorder characterized by deficiencies in hexosaminidase A enzyme activity. This particular test is not suitable for detecting Sandhoff disease. It is recommended when suspicion of Tay-Sachs disease remains high after primary tests indicate normal, indeterminate, or carrier status. It is especially useful in cases where blood sample collection poses a challenge, such as with infants.
Special Instructions
This test should not be ordered as a first-line test. It is only indicated after initial assays such as NAGR, NAGW, or NAGS show inconclusive results and clinical suspicion of Tay-Sachs disease persists. It requires fasting for 4 hours prior to specimen collection, with infants and small children samples collected before the next feeding. Ensure the healthcare professional provides their name and phone number with the requisition.
Limitations
This assay is not effective for detecting Sandhoff disease or GM2 activator deficiency. GM2 activator deficiency, presenting with similar clinical symptoms to Tay-Sachs and Sandhoff diseases, cannot be identified using this test as both hexosaminidase A and B levels remain normal in this condition. The test's performance characteristics comply with CLIA but have not received FDA clearance or approval, which may affect its acceptance or use in specific jurisdictions.
New York Approved
Methodology
Immunoassay (Fluorometric)
Biomarkers
LOINC Codes
- 2643-5
- 2643-5
Result Turnaround Time
2-8 days
Related Documents
For more information, please review the documents below
Specimen
Serum
Volume
1 mL
Minimum Volume
0.15 mL
Container
Serum gel
Collection Instructions
Centrifuge and aliquot serum into a plastic vial.
Patient Preparation
Fasting: 4 hours, required; Infants and small children should have specimen collected before next feeding/meal
Causes for Rejection
Gross hemolysis and lipemia are okay; other causes are not specified.
Stability Requirements
| Temperature | Period |
|---|---|
| Refrigerated | 5 days |
| Frozen | 365 days |