Tau/Aß42

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Also known as: Alzheimer Biomarkers
Formal name: Tau Protein and Amyloid Beta 42 Peptide
Related tests: Phosporylated Tau (P-tau), APOE Genotyping, PSEN1

At a Glance

Why Get Tested?

To help distinguish between Alzheimer disease and other forms of dementia

When to Get Tested?

These tests may be ordered along with cognitive and brain-imaging tests in people who demonstrate some form of dementia. These tests are not routine laboratory tests and are typically available only in research settings or memory clinics.

Sample Required?

A sample of cerebrospinal fluid collected using a spinal tap

Test Preparation Needed?

Your health practitioner will advise you of any preparatory requirements.

The Test Sample

What is being tested?

These tests measure amyloid beta 42 (Aß42) and tau protein in cerebrospinal fluid (CSF). Amyloid beta 42 is a peptide (protein fragment). Increased production of amyloid beta 42 in the brain can lead to the formation of senile plaques. Tau is a structural protein in the brain. When tau becomes saturated with phosphorus groups (P-tau), it can produce neurofibrillary tangles, twisted protein fragments that develop in neurons (nerve cells) and disrupt their ability to transport signals. Neurofibrillary tangles and senile plaques are considered to be the main diagnostic features of Alzheimer disease (AD) that are seen at autopsy.

The measurement of tau and Aß42 in CSF is being evaluated for potential roles in the diagnosis and monitoring of AD. It has been shown that a decrease in Aß42 with elevated tau or P-tau levels may predict the onset of AD.

How is the sample collected for testing?

A sample of cerebrospinal fluid is collected from the lower back using a lumbar puncture (spinal tap) procedure. This procedure is usually done in a hospital or clinic.

NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.

Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.

Is any test preparation needed to ensure the quality of the sample?

This is not a blood test but one that is performed on a sample of spinal fluid. Follow any preparatory instructions provided.

The Test

Common Questions

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Article Sources

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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.

Sources Used in Current Review

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