'Biomarkers' Could Spot Alzheimer's Disease Early, Studies Suggest 08/09/10
MONDAY, Aug. 9 (HealthDay News) -- The presence of three
proteins in cerebrospinal fluid may spot Alzheimer's disease long
before symptoms start and might also signal how fast the disease is
The findings, appearing in the August issue of the
Archives of Neurology, support recently released diagnostic criteria touting the use of such proteins, also known as biomarkers, in aiding diagnosis of this form of dementia.
"This just reinforces the recommendation by [Alzheimer's working groups] saying that biomarkers can actually be incorporated today into clinical practice in order to add a certain piece to the diagnosis if patients are already presenting with something that looks like Alzheimer's," said Maria C. Carrillo, senior director of medical and scientific relations at the Alzheimer's Association.
An accompanying editorial echoed that thought, by "strongly
commend[ing] CSF [cerebrospinal fluid] analyses of A1-42, T-tau,
and P-tau in circumstances where having a definitive diagnosis of
AD is important for counseling patients about such concerns as
work, driving, and making other lifestyle changes."
Scientists have been busily trying to find physiological
indications that can indicate if a person has Alzheimer's disease
or is going to develop it. Right now, effective medications against
Alzheimer's do not exist. However, the disease likely begins a
decade or so before symptoms appear, experts say, so spotting it
early might someday mean earlier (and therefore more effective)
prevention and treatment.
These researchers measured levels of three proteins - total tau
protein, phosphorylated tau and amyloid protein - in the
cerebrospinal (CSF) of 102 people with Alzheimer's, 200 people with
mild cognitive impairment and 114 "normal" individuals.
An "Alzheimer's disease signature" was present in 90 percent of
the Alzheimer's patients, 72 percent of those with mild cognitive
impairment (MCI) and 36 percent of those who had no cognitive
A signature consisting of low amyloid levels and high
phosphorylated tau levels identified patients with MCI who
progressed to Alzheimer's with 100 percent accuracy, the team
The fact that the signature was also found in individuals with
no sign of cognitive impairment underlines the likelihood that
Alzheimer's disease has started long before it is symptomatic,
stated the authors.
Another research group, this one set to report its finding in
the December print issue of the
Archives of Neurology verified that blood levels of the
beta-amyloid protein predict progression toward Alzheimer's --
another step towards identifying valid biomarkers for the
Patients who started out with high levels of the protein that
later tapered off, saw their cognitive health decline more rapidly,
even if they did not end up with full-blown Alzheimer's.
"High baseline levels of amyloid beta in combination with declining levels over time was sort of a high-risk profile for the development of Alzheimer's disease," explained study first author Stephanie Cosentino, an assistant professor of neuropsychology at Columbia University's Taub Institute in New York City.
The findings support the "amyloid cascade" theory of
Alzheimer's, "which points to the accumulate of amyloid in brain as
primary trigger for Alzheimer's disease," Cosentino said.
"This paper, which replicated an [earlier] study on these three risk genes indicates that ultimately, genetic biomarkers may play a very strong role in the whole spectrum of biomarkers [involved in Alzheimer's]," stated Carrillo, who was not involved with either study.
But, Cosentino cautioned, "amyloid beta is not ready to be used
as a disease biomarker. Not everyone who has high levels of plasma
amyloid beta will demonstrate Alzheimer's disease or cognitive
decline. Other factors need to be taken into account."
This marker may have more immediately utility in clinical
trials, as a way to determine if drugs-in-process are actually
effective, she said.
Association for more on this disease.
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