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- Hexosaminidase A Deficiency
Pre- and postnatal determination of Tay-Sachs disease carrier status; resolution of pseudodeficiency allele status
More than 95% of the mutant alleles in persons with Ashkenazi Jewish heritage are detected. In persons with French-Canadian ancestry, 80% of the mutations are detected, and 25% of mutations in non-Jewish Caucasians are also detected.
Polymerase chain reaction (PCR); primer extension; flow-sorted bead array analysis for five mutations and two pseudodeficiency alleles in the hexosaminidase A gene
Tay-Sachs disease is an autosomal recessive lysosomal storage disorder that causes progressive neurological deterioration ranging in severity from forms with infantile onset to those with adult onset. If the individual tested by DNA analysis is not of Ashkenazi Jewish descent, carrier testing by enzyme analysis is strongly recommended. Couples who are both carriers have a one in four risk of having a child with Tay-Sachs disease. DNA test results should be combined with enzyme test results and clinical information for the most accurate interpretation. The mutations tested include: 1278insTATC, G269S, IVS9+1 G>A, 1421+1 G>C, and 7.6 kb deletion. Pseudodeficiency alleles tested include: R247W and R249W.
Note: The pseudodeficiency mutation, R247W, accounts for 32% of enzyme-defined carriers in the non-Jewish population, while R249W accounts for 4% of pseudodeficiency among Ashkenazi Jews. These mutations affect the enzyme test, but do not affect in vivo function of beta-hexosaminidase A. Carriers of these mutations are not at increased risk to have children with Tay-Sachs disease.
Whole blood, amniotic fluid, chorionic villus sample (CVS) (submission of maternal blood is required for fetal testing), or LabCorp buccal swab kit (buccal swab collection kit contains instructions for use of a buccal swab)
7 mL whole blood, 10 mL amniotic fluid, 20 mg CVS, or LabCorp buccal swab kit
3 mL whole blood, 5 mL amniotic fluid, 10 mg CVS, or two buccal swabs
Maintain specimen at room temperature.
Causes for Rejection
Frozen specimen; hemolysis; quantity not sufficient for analysis; improper container; one buccal swab; wet buccal swab
A completed screening questionnaire must accompany specimens. Call 800-345-4363 to request forms, or photocopy the Tay-Sachs Disease Screening Questionnaire from the Genetics Appendix online.
|Order Code||Order Code Name||Order Loinc||Result Code||Result Code Name||UofM||Result LOINC|
|510404||Tay-Sachs, DNA Analysis||510407||Tay-Sachs, DNA||32632-2|
|510404||Tay-Sachs, DNA Analysis||511961||51969-4|