Alzheimer's Biomarkers- What ARE They?

In yesterday's post about the new Alzheimer Disease (AD) guidelines, I talked about how Alzheimer's biomarkers represent hope for future early diagnosis and treatment of AD. But what the heck ARE biomarkers? Today I will clarify...

Biomarkers - short for biological markers-are any naturally occurring substances in the body that reliably predict or indicate a disease. Cholesterol, for example, can be considered a biomarker for heart disease. We know when cholesterol levels are very high, it is likely that plaques of cholesterol could be building up in the heart arteries, making it more likely that that person could have a heart attack. In the case of Alzheimer's disease, the pathological changes in the brain involve the buildup of certain types of protein around the nerve cells in the brain, as well as degeneration and breakdown of other nerve cells. The combination of these two problems makes it hard for the brain to function correctly, as messages can't be passed effectively from one part of the brain to another.

Biomarkers for AD include beta-amyloid protein (that builds up in plaques) and tau protein, which is part of "neurofibrillary tangles"- clusters of protein that block nerve conduction. Right now, these proteins must be measured in spinal fluid, which means the patient must have a spinal tap (aka. lumbar puncture) which involves a needle in your back near your spinal cord. The hope is that measuring levels of these proteins in blood or urine may also prove to be accurate predictors of AD, so the more invasive procedure is not needed.

Not all of today's biomarkers require spinal fluid. Genetic testing for APOE-e4, as well as other genes that increase risk for AD, can be done by a simple blood test. Additionally, imaging of the brain using MRI and PET scans can provide valuable information as well.

Unfortunately, the diagnosis of Alzheimer's disease is not black and white, even with use of biomarkers and the new guidelines. I'll delve more into the challenges of diagnosis tomorrow.

BOTTOM LINE: Biomarkers for Alzheimer's include blood tests, spinal fluid tests and brain imaging, and these procedures are primarily restricted to research settings in 2011.

Breaking News about ALZHEIMER's

Over 5.4 million Americans suffer from Alzheimer's dementia (AD), and we believe that an equal number of people are in the early, yet UNdiagnosed stages of Alzheimer's. If you don't know someone affected yet, you will soon. My mother battled AD for over a decade, so I have a very personal face for this disease. For the first time in nearly three decades, there are new criteria for the diagnosis of this challenging disease. What's new?

Now there are THREE stages, with the first stage existing before there is any memory loss, called PRE-Clinical AD. This is based on research settings ONLY, where levels of biomarkers can be measured. The second stage is Mild Cognitive Impairment (MCI), where there are early memory and other cognitive changes, but these developments do not significantly impair the person's ability to perform daily tasks. The final stage is Dementia, where there are not only memory, orientation and judgement difficulties, but they are to a level that affects the patient's daily life.

Biomarkers represent a very exciting FUTURE for Alzheimer's disease research and treatment. Right now, these tests are not readily available to those of us in private practice, and even if they were, we have not established solid reference points to allow for accurate interpretation of the data. The importance is THIS- just like we can measure and treat cholesterol levels BEFORE someone has a heart attack, or see rising blood sugars before full diabetes, elevated AD biomarkers may warn us of impending AD. Obviously, the next step is then to develop medications that will PREVENT the full development of dementia, if they are started during the earliest stage.

We're making progress! Go to the Alzheimer Association website and see how you can help make a difference.

BOTTOM LINE: We are learning more and more about the early stages of Alzheimer's disease, and biomarkers represent an exciting new diagnostic tool...but they are still ONLY IN RESEARCH protocols.