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Biomarkers For Alzheimer's Disease

by Christine Kennard
for About.com

Updated: December 4, 2006

About.com Health's Disease and Condition content is reviewed by the Medical Review Board

Getting an Accurate Diagnosis for Alzheimer's

If a doctor sees a person with dementia we know through studies that 70% of them will have Alzheimer's disease. The only way at the present time to make a 100% accurate diagnosis of Alzheimer's is at autopsy when the various signs can be seen such as plaques and tangles and brain shrinkage. Biomarkers therefore are an additional tool for clinicians as there is currently no single test that can make an absolute diagnosis of Alzheimer's.

What is a biomarker?
A biomarker is "A specific physical trait used to measure or indicate the effects or progress of a disease or condition" The role of a biomarker is to provide doctors with an accurate and a reliable tool to make a diagnosis of Alzheimer's disease. With degenerative diseases such as Alzheimer's a biomarker should ideally, many doctors believe, meet a number of criteria. Biomarkers should be totally reliable, obtaining the sample should be simple, should have few side effects, and should be cheap.

Advantage of Biomarker's for Alzheimer's Disease
Any diagnostic tool that allows for earlier diagnosis of Alzheimer's disease means that treatment, closer monitoring and follow up can help the person with Alzheimer's disease and their caregivers. One of the problems of Alzheimer's disease is that symptoms of disease appear to develop only after substantial cell loss has occurred in brain. Effective biomarker tests could prevent such devastating damage occurring. This will be particularly important once a cure or more effective medications become available. Medications at present for Alzheimer's disease can only provide some short term improvements in cognitive function.

Current Biomarkers for Alzheimer's disease
Current biomarkers for Alzheimer's disease include:

  • Beta-amyloid measured in cerebrospinal fluid

  • Tau protein measured in cerebrospinal fluid

  • Neural thread protein/AD7C-NTP measured in cerebrospinal fluid and in urine.
  • In people with Alzheimer's disease their cerebrospinal fluid contains a reduced level of 42-amio-acid beta-amyloid and an increase in tau protein.

    Problem of Current Biomarker's for Alzheimer's

  • One of the problems is that as biomarkers for Alzheimer's are: Not totally reliable or accurate for a diagnosis of Alzheimer's as the same pattern findings are found in other conditions.

  • Costs involved in mass or individual screening are enormous. The current biomarkers, biological tests can only contribute to a diagnosis of Alzheimer's disease. There is no one test, one simple test, that gives an accurate diagnosis for Alzheimer's disease.

  • Some procedures are invasive and can be uncomfortable and are not without risk i.e. lumbar puncture test.
  • Article Sources Include: Alzheimer's Research Forum
    Jeffrey L. Cummings (2006) Major Biomarker Candidates for Alzheimer's Disease Explored Holds Promise for Improving the Diagnosis and Management of Dementia. University of California at Los Angeles. Journal of Alzheimer's Disease
    Marc E. Agronin (2004) Dementia A Practical Guide. Lippincott Williams & Wilkins

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