Test Code TSDP Tay-Sachs Disease, HEXA Mutation Analysis, Varies
Useful For
Carrier testing of individuals of Ashkenazi Jewish ancestry or who have a family history of Tay-Sachs disease
Determining Tay-Sachs disease carrier status for individuals with enzyme activity within the carrier or equivocal ranges
Prenatal diagnosis of Tay-Sachs disease for at-risk families
Confirmation of suspected clinical diagnosis of Tay-Sachs disease in individuals of Ashkenazi Jewish ancestry
Reflex Tests
Test ID | Reporting Name | Available Separately | Always Performed |
---|---|---|---|
CULFB | Fibroblast Culture for Genetic Test | Yes | No |
CULAF | Amniotic Fluid Culture/Genetic Test | Yes | No |
MATCC | Maternal Cell Contamination, B | Yes | No |
Testing Algorithm
For prenatal specimens only: If amniotic fluid (nonconfluent cultured cells) is received, amniotic fluid culture/genetic test will be added and charged separately. If chorionic villus specimen (nonconfluent cultured cells) is received, fibroblast culture for genetic test will be added and charged separately. For any prenatal specimen that is received, maternal cell contamination studies will be added.
The following algorithms are available in Special Instructions:Â Â Â Â Â
-Tay-Sachs Disease Carrier Testing Protocol
-Tay-Sachs and Related Disorders Diagnostic Testing Algorithm
Special Instructions
Method Name
Polymerase Chain Reaction (PCR) Analysis
Reporting Name
Tay-Sachs, Mutation AnalysisSpecimen Type
VariesAdditional Testing Requirements
All prenatal specimens must be accompanied by a maternal blood specimen.
-Order MATCC / Maternal Cell Contamination, Molecular Analysis on the maternal specimen.
Shipping Instructions
Specimen preferred to arrive within 96 hours of collection.
Prenatal specimens can be sent Monday through Thursday and must be received by 5 p.m. CST on Friday in order to be processed appropriately.
Specimen Required
Patient Preparation: A previous bone marrow transplant from an allogenic donor will interfere with testing. Call 800-533-1710 for instructions for testing patients who have received a bone marrow transplant.
Submit only 1 of the following specimens:
Specimen Type: Whole blood
Container/Tube:
Preferred: Yellow top (ACD)
Acceptable: Any anticoagulant
Specimen Volume: 2.6 mL
Collection Instructions:
1. Invert several times to mix blood.
2. Send specimen in original tube.
Specimen Stability Information: Ambient (preferred)/Refrigerated/Frozen
Prenatal Specimens
Due to the complexity of prenatal testing, consultation with the laboratory is required for all prenatal testing.
Specimen Type: Amniotic fluid
Container/Tube: Amniotic fluid container
Specimen Volume: 20 mL
Specimen Stability Information: Refrigerated (preferred)/Ambient
Specimen Type: Chorionic villi
Container/Tube: 15-mL tube containing 15 mL of transport media
Specimen Volume: 20 mg
Specimen Stability Information: Refrigerated
Acceptable:
Specimen Type: Confluent cultured cells
Container/Tube: T-25 flask
Specimen Volume: 2 Flasks
Collection Instructions: Submit confluent cultured cells from another laboratory.
Specimen Stability Information: Ambient (preferred)/Refrigerated
Specimen Minimum Volume
Blood: 0.5 mL
Amniotic Fluid: 10 mL
Chorionic Villi: 5 mg
Specimen Stability Information
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Varies | Varies |
Reject Due To
All specimens will be evaluated by Mayo Clinic Laboratories for test suitability.Clinical Information
Tay-Sachs disease is caused by an absence of hexosaminidase (Hex A) enzyme activity, which results in the accumulation of the sphingolipid GM2 ganglioside. Mutations within the alpha subunit of the hexosaminidase A gene, HEXA, cause the clinical manifestations associated with Tay-Sachs disease (TSD). The classic form of TSD becomes apparent in infancy when mild motor weakness is noted along with impaired visual acuity and the presence of a "startle response." Other manifestations of this condition include progressive neurodegeneration, seizures, and blindness leading to total incapacitation and death. Other types of TSD (eg, subacute and adult onset) are characterized by later ages of onset and death. The symptoms and severity of disease vary widely.
TSD is inherited in an autosomal recessive manner. The carrier frequency for TSD disease in the Ashkenazi Jewish population is 1/31. This panel tests for the 3 common mutations in the Ashkenazi Jewish population: 1278insTATC, G269S, and IVS12+1G->C. When performed in conjunction with hexosaminidase A biochemical testing, the mutation detection rate using this assay is approximately 99%. Also included in this analysis are the mutations IVS9+1G->A and 7.6 kb, del 5'UTR-IVS+1 that are over-represented in individuals of Celtic or French Canadian ancestry, respectively.
A common cause of false-positive carrier screening by enzyme analysis, particularly among individuals of non-Ashkenazi Jewish descent, is due to the presence of a pseudodeficiency allele, either R247W or R249W. These sequence variations are not associated with disease, but result in the production of a hexosaminidase A enzyme with decreased activity towards the artificial substrate used in the enzyme assay. Both pseudodeficiency alleles are evaluated for by this panel.
The recommended first-tier test to screen for TSD is biochemical analysis measuring hexosaminidase enzyme activity, NAGW / Hexosaminidase A and Total Hexosaminidase, Leukocytes. Molecular tests form the basis of confirmatory diagnostic or carrier testing. See Tay-Sachs Disease Carrier Testing Protocol in Special Instructions for additional information.
Alternatively, full gene sequencing is available to evaluate for mutations in all coding regions and exon/intron boundaries of the HEXA gene by ordering HEXAZ / Tay-Sachs Disease, HEXA Gene, Full Gene Analysis.
Reference Values
An interpretive report will be provided.
Day(s) and Time(s) Performed
Tuesday; 10 a.m.
Analytic Time
9 daysPerforming Laboratory

Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.CPT Code Information
81255-HEXA (hexosaminidase A, alpha polypeptide) (eg, Tay-Sachs disease) gene analysis, common variants (eg, 1278insTATC, 1421+1G->C, G269S)
Fibroblast Culture for Genetic Test
88233-Tissue culture, skin or solid tissue biopsy (if appropriate)
88240-Cryopreservation (if appropriate)
Amniotic Fluid Culture/Genetic Test
88235-Tissue culture for amniotic fluid (if appropriate)
88240-Cryopreservation (if appropriate)
Maternal Cell Contamination, B
81265-Comparative analysis using Short Tandem Repeat (STR) markers; patient and comparative specimen (eg, pre-transplant recipient and donor germline testing, post-transplant non-hematopoietic recipient germline [eg, buccal swab or other germline tissue sample] and donor testing, twin zygosity testing or maternal cell contamination of fetal cells (if appropriate)
LOINC Code Information
Test ID | Test Order Name | Order LOINC Value |
---|---|---|
TSDP | Tay-Sachs, Mutation Analysis | 51773-0 |
Result ID | Test Result Name | Result LOINC Value |
---|---|---|
53185 | Result Summary | 50397-9 |
53186 | Result | 51773-0 |
53187 | Interpretation | 69047-9 |
53188 | Reason for Referral | 42349-1 |
53189 | Specimen | 31208-2 |
53190 | Source | 31208-2 |
53191 | Released By | 18771-6 |
NY State Approved
YesForms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Molecular Genetics: Biochemical Disorders Patient Information (T527) in Special Instructions