TUESDAY, April 5 (HealthDay News) -- New research shows that
levels of a particular protein can indicate the severity of
Alzheimer's disease, but it doesn't serve as an early warning sign
of the illness.
Still, the findings are helpful because they reveal that signs
of Alzheimer's lurk in the blood, said one of the co-authors of the
"What's promising is that we can get such clear signals" through an indicator known as a biomarker, said Monique Breteler, an epidemiologist with University Medical Center Rotterdam in the Netherlands. "It will be a matter of time, and resources, to find the markers or panels of markers in blood that can be used to help predict or diagnose the disease."
Alzheimer's disease, which robs its victims of their memories,
affects an estimated 5.2 million people in the United States. That
number is expected to grow to as many as 7.7 million Americans by
2030 as the population ages.
At the moment, physicians can't diagnose Alzheimer's with
certainty in living patients; it can only be diagnosed with
certainty after death.
Scientists have known for some time that there are higher levels
of a protein called clusterin in the blood of people with
Alzheimer's, Breteler said, and recent research has linked
variations in the protein to the disease. Those findings, in turn,
raise the prospect that the protein could actually be a factor in
causing Alzheimer's, she said. If so, physicians might be able to
diagnose the disease early on and maybe even try to stop it in its
Unfortunately, the new study revealed the limitations of
From 1997-99, researchers tested levels of the protein in 60
people with Alzheimer's and a randomly chosen group of 926 people,
and additionally, in 156 people diagnosed with Alzheimer's before
2007. They found that those with the highest levels of clusterin
were also most likely to have Alzheimer's even after they adjusted
statistics so they wouldn't be thrown off by factors such as age,
education level and gender. Alzheimer's patients with the highest
levels had the worst disease.
At the moment, one potential use for a clusterin blood test
would be to predict rapid decline in Alzheimer's patients, said
Greg Cole, associate director of the Alzheimer's Center at the
University of California Los Angeles. "But," he said, "I don't
think it is ready for that use."
Dr. James R. Burke, director of the Memory Disorders Clinic at
Duke University Medical Center, identified a potential problem with
such a test: clusterin levels don't specify whether a person has
Alzheimer's disease or vascular dementia, a form of senility
related to impaired blood flow, Burke said. "So, measurements of
clusterin do not appear to be useful clinically," he noted.
Even so, research like this latest study is "important to
prevent widespread adoption of tests that are not useful to answer
clinical questions, such as, 'Am I going to get Alzheimer's
disease?'" he added.
The study appears in the April 6 issue of the
Journal of the American Medical Association.
For more about
Alzheimer's disease, try the U.S. National Library of Medicine.
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