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 Such a test could initially be used to select patients for
clinical trials of experimental treatments being developed to try to
halt progression of Alzheimer's, the researchers said, and may one
day move into routine use in doctors' clinics.
"Alzheimer's begins to affect the brain many years before patients
are diagnosed (and) many of our drug trials fail because by the time
patients are given the drugs the brain has already been too severely
affected," said Simon Lovestone of Oxford University, who led this
work from King's College London.
"A simple blood test could help us identify patients at a much
earlier stage to take part in new trials and hopefully develop
treatments," he said.
Shares in biotech company Proteome Sciences, which co-authored the
study with scientists from King's College, jumped 12 percent on the
news on Tuesday morning.
Alzheimer's is the most common form of dementia, a brain-wasting
disease which in 2010 was estimated to be costing the world $604
billion a year. The fatal disease affects 44 million people
worldwide, with the number set to triple by 2050, the campaign group
Alzheimer's Disease International says.
Several big pharma firms including Roche, Eli Lilly, Merck & Co and
Johnson & Johnson, are pursuing various approaches to get to the
root cause of Alzheimer's and try to find treatments to halt its
progression.
Yet over the past 15 years, more than 100 experimental Alzheimer's
drugs have failed in trial. Lovestone and other experts believe this
may be because drug trials are conducted too late, in patients whose
condition has already gone too far.
A predictive test for use before people develop symptoms would help
researchers select the right people for drug trials, and help show
whether the experimental drugs are working.
SEARCH FOR ALTERNATIVE TEST
Previous studies have found that PET brain scans and tests of lumbar
fluid can be used to predict the onset of dementia from people with
a less severe condition known as mild cognitive impairment (MCI),
but these tests are expensive and invasive, so scientists are keen
to develop a cheaper, simpler blood test.
MCI includes problems with day-to-day memory, language and
attention. It can be an early sign of dementia, or a symptom of
stress or anxiety.
Around 10 percent of people diagnosed with MCI develop dementia
within a year. Apart from regular assessments to measure memory
decline, there is currently no accurate way of predicting who will
or won't develop dementia.
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For this study, published in the journal Alzheimer's & Dementia,
Lovestone's team used blood samples from 1,148 people - 476 with
Alzheimer's, 220 with mild cognitive impairment and 452 elderly
controls without dementia. They were analysed for 26 proteins
previously found to be linked with Alzheimer's. The team found 16
of these 26 proteins to be strongly associated with brain shrinkage
in either MCI or Alzheimer's and then ran a second series of tests
to see which of these could predict which patients would progress
from MCI to Alzheimer's.
With this second series, they found a combination of 10 proteins
capable of predicting with 87 percent accuracy whether people with
MCI would develop Alzheimer's disease within a year.
Experts in the field welcomed the results but said they should be
replicated in larger studies before an Alzheimer's blood test could
be rolled out for use in doctors' clinics.
"The results reported today are interesting, but as the authors
point out there is still a very large amount of work remaining until
a usable blood test for Alzheimer's disease becomes available," said
Adrian Pini of the MRC Centre for Developmental Neurobiology at
King's College London.
James Pickett, head of research at the Alzheimer's Society, said the
research "does not mean that a blood test for dementia is just
around the corner".
"These 10 proteins can predict conversion to dementia with less than
90 percent accuracy, meaning one in 10 people would get an incorrect
result," he said. "Accuracy would need to be improved before it
could be a useful diagnostic test."
 (Additional reporting by Ben Hirschler; Editing by Tom Heneghan and
Jason Neely)
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