The most common Tay-Sachs testing method is a blood test that looks for mutations in a specific gene. If both parents are carriers, they may want to consult with a genetic counselor for help in deciding whether to conceive. Another common form of Tay-Sachs testing is a prenatal test, which involves either removing a piece of the placenta or sampling the fluid surrounding the baby.
Tay-Sachs disease can be identified through a simple blood test that measures beta-hexosaminidase A (HEXA) activity.
This blood test looks for specific mutations, or changes, in the gene that codes for HEXA. Since 1985, when the gene was first isolated, over 50 different mutations in this gene have been identified. However, some mutations are still unknown. Current Tay-Sachs testing methods detect about 95 percent of carriers of Ashkenazi Jewish background and about 60 percent of carriers in the general population.
If both parents are carriers, they may want to consult with a genetic counselor for help in deciding whether to conceive or whether to have a fetus that has tested positive for Tay-Sachs. Extensive carrier testing of Ashkenazi Jews has significantly reduced the number of Tay-Sachs children in this population group. Today, most cases of Tay-Sachs disease occur in populations not thought to be at high risk.
Prenatal testing for Tay-Sachs can be done when a woman is 11 weeks pregnant using CVS (chorionic villi sampling). This involves removing a tiny piece of the placenta. The fetus can also be tested through amniocentesis when a woman is 16 weeks pregnant. In this procedure, a needle is used to take a sample of the fluid surrounding the baby to test it.
Assisted reproductive therapy is an option for carriers who don't want to risk giving birth to a child with Tay-Sachs. A new technique used in conjunction with in-vitro fertilization enables parents who are Tay-Sachs carriers to give birth to healthy babies. Embryos created in-vitro are tested for Tay-Sachs before being implanted into the mother, allowing only healthy embryos to be selected.