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Tay-Sachs Disease Mutation Analysis

CPT:

81255

Tay-Sachs disease occurs at an increased frequency in individuals of Ashkenazi Jewish and French-Canadian descent. It is a lysosomal storage disorder that results in untreatable neurological degeneration and, in the common infantile form, death by 5 years of age.

Test Details

Use

Tay-Sachs disease mutation analysis tests for 8 mutations (6 disease-causing mutations and 2 pseudodeficiency alleles). We perform Tay-Sachs enzyme analysis (hexosaminidase A) in conjunction with Tay-Sachs mutation analysis to provide a carrier detection rate of 97–98% in the Ashkenazi Jewish population. disease occurs at an increased frequency in individuals of Ashkenazi Jewish and French-Canadian descent. It is a lysosomal storage disorder that results in untreatable neurological degeneration and, in the common infantile form, death by 5 years of age.

 

Synonyms

Hexosaminidase A Deficiency;

Test Includes

Mutation(s) include: c.-2564_253+5128del7945insG  (legacy name: 7.6kb deletion); c.739C>T (p.R247W); c.745C>T (p.R249W); c.805G>A (p.G269S); c.1073+1G>A; c.1274_1277dupTATC (p.Y427fs) (legacy name: +TATC1278);  c.1421+1G>C

Methodology

Polymerase chain reaction (PCR); primer extension; flow-sorted bead array analysis

Turnaround Time

10-14 days (when cell culture is required, add ~2 weeks) 

Pregnancy Week

0–13 Weeks
14–21 Weeks
22+ Weeks

Discipline Code

MG (Molecular Genetics)

Specimen Requirements

Specimen

Whole blood or mouthwash (see specimen kit for detailed instructions), amniotic fluid, chorionic villi

Volume

Postnatal:  10 mL whole blood or mouthwash / Prenatal: 10 mL amniotic fluid in orange-top polypropylene tube, 10-15 mg chorionic villi in laboratory provided screw-top tubes with sterile transport medium or one T-25 flask of confluent cells. 

Container

Lavender-top (EDTA) tube or yellow-top (ACD-A) tube or mouthwash kit

Collection

Mouthwash collection:  Patient should not eat, drink, smoke or chew gum for at least one hour prior to collection. (See specimen kit for detailed instructions). 

Mouthwash samples can be sent when ordering up to two tests. When ordering more than two tests, blood samples are required.  10 mL of Scope® mouthwash that has been swished vigorously for at least 1 minute. Collect in orange-top 50 mL polypropylene tube. 

Special Instructions

Prenatal testing: Integrated Genetics clients should call 800-848-4436 to speak to a laboratory genetic coordinator before collecting any specimens.   In some circumstances, specimens from other family members may be required. 

All prenatal specimens (including cord blood) must be accompanied by a maternal blood or mouthwash specimen for analysis of possible maternal cell contamination. 

Discard first 2 mL; then 10 mL amniotic fluid in 15 mL orange-top polypropylene tube, 10-15 mg chorionic villi in laboratory-provided screw-top tubes with sterile transport medium or one T-25 flask of confluent cells. 

Additional sample must be obtained for back-up culture at one of our cytogenetics laboratories or another facility.  If additional testing is desired, more amniotic fluid is needed. For example, chromosome analysis requires an additional 15-25 mL (see Cytogenetics – Amniotic Fluid Chromosome Analysis test page) and AFAFP requires an additional 2 mL (see Amniotic Fluid Alpha-Fetoprotein - AFAFP test page).  

Causes for Rejection

Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; unlabeled or mislabeled specimen

Storage Instructions

Maintain specimen at room temperature.

Additional Information

Couples who are planning a pregnancy or who are already pregnant may decide to have testing to find out if they are carriers and at risk of having a baby with Tay-Sachs disease. It is standard of care to offer carrier screening to individuals of Ashkenazi Jewish descent for Bloom syndrome, Canavan disease, cystic fibrosis, familial dysautonomiaFanconi anemia group C, Gaucher disease, mucolipidosis type IV, Niemann-Pick disease type A and Tay-Sachs disease. If both parents are found to be carriers, prenatal diagnosis by CVS or amniocentesis is available. Our Tay-Sachs disease mutation analysis tests for 8 mutations (6 disease-causing mutations and 2 pseudodeficiency alleles). We perform Tay-Sachs enzyme analysis (hexosaminidase A) in conjunction with Tay-Sachs mutation analysis to provide a carrier detection rate of 97–98% in the Ashkenazi Jewish population.

Limitations

False-positive and false-negative results may occur for reasons that include genetic variants, blood transfusions, bone marrow transplantation, erroneous representation of family relationships, or contamination of a fetal sample with maternal cells.

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