At a Glance
Why Get Tested?
When to Get Tested?
These tests may be ordered along with cognitive and brain-imaging tests in patients who demonstrate some form of dementia. These tests are not routine laboratory tests and are available only in research settings or memory clinics.
A sample of cerebrospinal fluid collected using a spinal tap
Test Preparation Needed?
Your doctor will advise you of any preparatory requirements.
The Test Sample
What is being tested?
Amyloid beta 42 is a peptide that can undergo increased production resulting in a collection of senile plaques in the brain. Tau is a structural protein of the brain that, when changed chemically (becomes saturated with phosphorus groups, P-tau), can create neurofibrillary tangles, twisted protein fragments that develop in neurons that disrupt their ability to transport signals. These tangles in conjunction with the plaques are considered to be the main diagnostic features of Alzheimer's Disease (AD) 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?
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?
Your physician will advise you of any preparatory requirements. This is not a blood test but one on spinal fluid. Lumbar punctures are usually done in a hospital setting.
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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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Lawrence Mayer, MD, PhD. Professor, Department of Psychiatry and Behavioral Sciences, Johns Hopkins School of Medicine, Baltimore, MD.
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