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Tay-Sachs Disease (HEXA), 7 Variants
0051428
Ordering Recommendation

Confirm common pathogenic and pseudodeficiency HEXA gene variants in Ashkenazi Jews and French Canadians with abnormal levels of HEX A enzyme. For initial testing of Tay-Sachs disease, refer to 2008125 Hexosaminidase A percent and Total Hexosaminidase in Leukocytes.

Mnemonic
HEXA
Methodology
Polymerase Chain Reaction/Fluorescence Monitoring
Performed
Tue, Fri
Reported
5-10 days
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
ARUP Consult®
Disease Topics
Specimen Required
Patient Preparation
 
Collect
Lavender (EDTA), pink (K2EDTA), or yellow (ACD Solution A or B). 
Specimen Preparation
Transport 3 mL whole blood. (Min: 1 mL) 
Storage/Transport Temperature
Refrigerated. 
Unacceptable Conditions
Specimens collected in sodium heparin or lithium heparin tubes. 
Remarks
 
Stability
Ambient: 72 hours; Refrigerated: 2 weeks; Frozen: 1 month 
Reference Interval
By report
Interpretive Data
Background information for Tay-Sachs Disease (HEXA), 7 Variants:
Characteristics:
Tay-Sachs disease is a lysosomal storage disease that, in the most severe childhood-onset form, leads to a loss of motor skills beginning at 3-to 6-months of age and progresses to blindness, seizures, total incapacitation, and eventual death by 4 years of age. Adult-onset Tay-Sachs is a milder disease with later onset and slower progression. In adults, Tay-Sachs disease is associated with variable neurological findings, including progressive dystonia, spinocerebellar degeneration, motor neuron disease, and bipolar form of psychosis.
Incidence:
1 in 3000 Ashkenazi Jewish individuals.
Inheritance:
Autosomal recessive.
Cause:
HEXA gene pathogenic variants.
Variants Tested:
Four pathogenic 7.6kb del, c.1073+1G>A, p.Y427Ifs (c.1274_1277dup TATC), c.1421+1G>C; one mild pathogenic p.G269S (c.805G>A); and two pseudodeficiency alleles p.R247W (c.739C>T) and p.R249W (c.745C>T).
Clinical Sensitivity:
94 percent in Ashkenazi Jewish individuals, 59 percent in other ethnicities.
Methodology:
Polymerase chain reaction (PCR) and fluorescence monitoring.
Analytical Sensitivity and Specificity:
Greater than 99 percent.
Limitations:
HEXAvariants other than those specified above will not be detected. Diagnostic errors can occur due to rare sequence variations.

Compliance Statement C: The performance characteristics of this test were validated by ARUP Laboratories. The U.S. Food and Drug Administration (FDA) has not approved or cleared this test. However, FDA approval or clearance is currently not required for clinical use of this test. The results are not intended to be used as the sole means for clinical diagnosis or patient management decisions. ARUP is authorized under Clinical Laboratory Improvement Amendments (CLIA) and by all states to perform high-complexity testing. Counseling and informed consent are recommended for genetic testing. Consent forms are available online.

Note
CPT Code(s)
81255
Components
Component Test Code*Component Chart NameLOINC
0051430Tay-Sachs Disease (HEXA), Allele 138900-7
0051431Tay-Sachs Disease (HEXA), Allele 238900-7
0051432Tay-Sachs Disease (HEXA), Interpretation51773-0
2001315Tay-Sachs Disease (HEXA), Specimen31208-2
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
Aliases
  • Hexosaminidase A
  • Hexosaminidase A Deficiency DNA assay
  • TSD molecular assay