Alzheimer's disease spotted earlier with new tests
Published Thursday, July 16, 2009 12:10PM EDT
New tests that assess brain changes could one day help diagnose Alzheimer's disease at its earliest stages, researchers report.
In one study, researchers in Ireland measured brain volume and used a combination of memory tests to accurately identify 94 per cent of people who had progressed from mild cognitive impairment to early Alzheimer's disease.
In another study, U.S. researchers found that a brain scan that measures glucose, along with results from memory tests also accurately predicted disease progression.
The findings were presented at the Alzheimer's Association 2009 International Conference on Alzheimer's Disease, in Vienna.
While it is fairly simple to identify mild cognitive impairment using neurological and memory tests, the only sure way to accurately diagnose Alzheimer's is through an autopsy that looks for the disease's hallmark plaques and tangles in the brain.
Identifying those in the early stages of Alzheimer's could allow doctors help patients access therapies sooner that can delay the onset of the memory-robbing disease.
In the Irish study, Michael Ewers of Trinity College Dublin and colleagues studied 345 participants who were either healthy, had mild cognitive impairment or who had Alzheimer's. All the patients were part of the U.S. National Institute on Aging's Alzheimer's Disease Neuroimaging Initiative, or ADNI.
The researchers looked at an array of tests and found three memory tests plus MRI measurements of brain volume in the left hippocampus -- a region that plays a role in memory -- were most predictive of disease progression.
The memory tests were 89.9 per cent accurate in identifying those with mild cognitive impairment who had progressed to Alzheimer's (of which there were 50 people who converted over the next year and a half).
By adding in results from the MRI hippocampus volume measurements, they could increase classification accuracy to 94 per cent.
When the same set of tests was applied to distinguish healthy people from those with Alzheimer's, classification accuracy was 95.7 per cent.
"The clinical symptoms of MCI alone are not enough to allow for early diagnosis of Alzheimer's," Ewers said in a statement.
"In fact, a substantial proportion of people with MCI may revert back to normal or may not develop Alzheimer's for years. Thus, the challenging task is to discern which of people with MCI have the Alzheimer's brain changes that may be responsible for their initial memory and thinking problems and their eventual progression to Alzheimer's, so that they can be targeted for Alzheimer's-specific treatments."
In a separate study, Susan Landau of the University of California, Berkeley used data on 85 patients and found PET (positron emission tomography) scans that measure glucose in the brain and poor memory recall were strong predictors.
People who did poorly on these measures were 15 times more likely to progress to Alzheimer's within two years.
"People who did poorly on those two measurements - that is, low glucose metabolism combined with poor memory performance - were 15 times more likely to convert to Alzheimer's compared to individuals who were normal on those measurements," Landau said in a statement.
According to the researchers, finding the biological markers of early Alzheimer's will be critical in identifying patients most likely to experience Alzheimer's over time. It'll also help find those , and patients who would be good candidate for clinical studies on Alzheimer's drug treatments.
"With the continued aging of the population and the growing epidemic of Alzheimer's, early detection of the disease is crucial for risk assessment, testing new therapies, and eventual early intervention with better drugs, once they are developed," said Dr. Ronald Petersen, chair of the Alzheimer's Association Medical & Scientific Advisory Council.
"It is critical to identify affected individuals while they are still relatively cognitively healthy so that future therapies can preserve healthy memory and thinking function."