Hexosaminidase

This is a blood test which is used in detecting Tay-Sachs disease and Sandhoff disease. These are diseases in which there is brain deterioration which causes mental and physical retardation, blindness, red spots on the skin, spasticity of the muscles and convulsions. Enlargement of the head may be present. There are two different enzymes that are tested for:

  • Hexosaminidase A, in which a deficiency results in Tay-Sach's disease

  • Hexosaminidase A and B, in which a deficiency results in Sandhoff's disease (an uncommon variation of Tay-Sachs disease).

Tay Sachs is a genetic disease that is usually found at a very young age with death usually occurring by the age of 4. The test is usually done on both parents to determine the genetic identifying carriers of the disease.

PREPARATION FOR TEST

No preparation or fasting is necessary.

NORMAL FINDINGS

  • Hexosaminidase A: 7.5-9.8 U/L (SI units)

  • Total hexosaminidase: 9.9-15.9 U/L (SI units)

(Check with the lab due to a wide variety of testing methods)

Ranges for normal findings may vary among different laboratories and hospitals. You should always check with your doctor after having lab work or other tests done to discuss the meaning of your test results and whether your values are considered within normal limits.

ABNORMAL FINDINGS

  • Decreased hexosaminidase A: Tay Sachs disease

  • Decreased hexosaminidase A and B: Sandhoff's disease

MEANING OF TEST

Your caregiver will go over the test results with you and discuss the importance and meaning of your results, as well as treatment options and the need for additional tests if necessary.

OBTAINING THE TEST RESULTS

It is your responsibility to obtain your test results. Ask the lab or department performing the test when and how you will get your results.