If your baby is suspected of having Tay-Sachs disease, a physical examination may reveal or confirm symptoms of the disease. A blood test (Tay-Sachs screen test) can determine whether your baby's body is producing the enzyme hexosaminidase A (hex A). The blood sample can be taken from a vein or from the umbilical cord immediately after birth.

If you are pregnant and are at risk for having a child with Tay-Sachs disease, the Tay-Sachs screen test can be done. A blood sample is collected from the placenta during chorionic villus sampling, or a sample of amniotic fluid is collected during amniocentesis. For more information, see the topics Amniocentesis and Chorionic Villus Sampling.

The Tay-Sachs screen test is also used to confirm late-onset Tay-Sachs disease in a teen or adult with symptoms of the disease.

A positive Tay-Sachs test may need to be confirmed with other genetic tests. For more information, see the medical test Genetic Test.

Screening for carriers

Knowing whether you are a carrier of Tay-Sachs disease is important because Tay-Sachs is an autosomal recessive disease. You have one gene that produces hex A and one that does not produce this enzyme. Your body probably makes about half of the normal level of hex A, which prevents you from getting the disease. But you can pass the gene on to your children. If both you and your partner are carriers, there is a 1-in-4 chance (25%) that any child you have will have Tay-Sachs disease.

If you are considering having a child, the American College of Obstetricians and Gynecologists (ACOG) recommends that:³

• Both prospective parents be screened if both of you are Ashkenazi Jews or of French-Canadian or Cajun descent or have a family history of the disease. If both of you test positive as carriers, you should consider genetic counseling.
• You or your partner be screened if either of you is an Ashkenazi Jew or of French-Canadian or Cajun descent or has a family history of the disease. If one of you tests positive for being a carrier, the other partner should be screened.

Either hex A testing or DNA testing can be done.

In Ashkenazi Jews:³

• DNA testing detects 94 out 100 carriers.
• Hex A testing detects 98 out of 100 carriers.