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The test for Tay-Sachs disease measures the amount of an enzyme called hexosaminidase A (hex A) in the blood. Hex A breaks down fatty substances in the brain and nerves. Tay-Sachs is an inherited disease in which the body can't break down fatty substances as it should, so the fatty substances collect in the nerve cells of the brain and damage them.
Tay-Sachs can occur when parents pass on a changed gene to their child.
A Tay-Sachs test may also measure the amount of another enzyme, called hexosaminidase B. People who cannot make both hex A and B have a condition called Sandhoff disease.
The Tay-Sachs enzyme test is usually done on blood taken from a vein or from the umbilical cord right after birth.
A test to measure hexosaminidase A is done to:
You do not need to do anything before having this test. If you are having this test to see whether you are a Tay-Sachs carrier, you should tell your doctor if you have had a blood transfusion in the past 3 months.
Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results may mean.
A health professional uses a needle to take a blood sample, usually from the arm.
When a blood sample is taken, you may feel nothing at all from the needle. Or you might feel a quick sting or pinch.
There is very little chance of having a problem from this test. When a blood sample is taken, a small bruise may form at the site.
Each lab has a different range for what's normal. Your lab report should show the range that your lab uses for each test. The normal range is just a guide. Your doctor will also look at your results based on your age, health, and other factors. A value that isn't in the normal range may still be normal for you.
CitationsWilson RD, et al. (2016). Joint SOGC–CCMG opinion for reproductive genetic carrier screening: An update for all Canadian providers of maternity and reproductive healthcare in the era of direct-to-consumer testing. Journal of Obstetrics and Gynaecology Canada, 38(8): 742–762.e3. DOI: 10.1016/j.jogc.2016.06.008. Accessed October 6, 2020.
Adaptation Date: 8/16/2021
Adapted By: Alberta Health Services
Adaptation Reviewed By: Alberta Health Services
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