Tau/A-beta-42

Does this test have other names?

Tau protein and amyloid beta 42 peptide test, Alzheimer disease biomarkers

What is this test?

This test checks for proteins in the cerebrospinal fluid (CSF) to help healthcare providers diagnose Alzheimer disease. It helps tell the difference between Alzheimer disease and other forms of dementia. CSF is the fluid surrounding your brain and spinal cord. A low level of a protein called beta amyloid and a high level of a protein called tau may be linked to Alzheimer disease.

Why do I need this test?

You may need this test if you have symptoms of Alzheimer disease. Alzheimer disease causes changes in thinking and behavior. Symptoms include:

• Memory loss

• Changes in mood and personality

• Decreased ability to do daily tasks

What other tests might I have along with this test?

No test can definitively indicate Alzheimer disease. Testing for protein levels in your CSF along with physical and mental exams help healthcare providers diagnose Alzheimer disease. You may also have a brain scan to make images of your brain.

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

If you have symptoms of Alzheimer disease, low levels of beta amyloid protein, and high levels of tau protein, your healthcare provider may suspect Alzheimer disease.

How is this test done?

This test requires a sample of CSF. It's taken through a lumbar puncture in your lower back. During this procedure, you either sit up and lean forward or lie down on your side. A healthcare provider inserts a needle into your spine and draws out a sample of fluid to be analyzed at a lab.

Does this test pose any risks?

A lumbar puncture is a safe procedure, but there are some possible risks. The most common risks are:

• Back pain

• Headache

• Bleeding

• Infection

• Numbness 

Discuss these risks with your healthcare provider before the procedure.

What might affect my test results?

Depending on where your testing is done, your results may be different from other people's results. That's because this type of testing is still new, and research needs to be done to standardize test numbers and techniques.

How do I get ready for this test?

You usually don't need to prepare for this test. Tell your healthcare provider if you have a history of bleeding. You may need to lie down for a while after the test. Ask how much time you should allow for the test and recovery. In addition, be sure your provider knows about all the medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.