Tau/Aß42
Also known as: Alzheimer biomarkers
Formal name: Tau protein and Amyloid Beta 42 peptide
Related tests: Phosporylated Tau (P-tau), Apolipoprotein E genotyping (ApoE), Presenilin 1 (PSEN1)
The Test
How is it used?
Tests for Tau protein and Aß42 may be used as supplemental tests to help establish a diagnosis of Alzheimer's Disease.
If someone has symptoms of dementia, such as memory loss, behavioral changes, and decreased ability to perform daily life functions, the doctor will do a thorough work-up to try to determine the cause. This work-up may include a variety of cognitive tests (Minimal Mental State Exam) to assess memory and possibly PET scanning tests (Pittsburgh Compound-B) of the brain to look for abnormalities.
When is it ordered?
Tau protein and Aß42 tests are primarily performed in research settings and in some memory clinics in conjunction with cognitive tests and brain scans. Some doctors may order them outside of these settings; however, information on how to interpret the results is limited.
What does the test result mean?
In a symptomatic patient, a low Aß42 CSF level along with a high tau level reflects an increased likelihood of Alzheimer's Disease. Recent studies have shown that these abnormal levels may predict a rapid progression of AD. Since these are still in a research phase and not part of routine examinations, it is unclear as to whether all who might have abnormal results would definitely have AD.
Is there anything else I should know?
Assessments of Aß42 and tau protein levels do not singularly establish a diagnosis of Alzheimer's Disease; they represent a common finding that may be used in conjunction with other tests and the patient's clinical and family history to suggest a diagnosis of AD.
The clinical use of these tests continues to evolve. For instance, multiple variants of amyloid beta protein, such as Aß40 and Aß38, have been identified and are being researched for their potential use as AD biomarkers.
