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Early Alzheimer’s Tests Show Promise

Tests Could Allow Detection, Treatment Before Symptoms Arise
By
WebMD Health News
Reviewed by Louise Chang, MD

June 12, 2007 -- Research appears to be moving closer to developing early tests for Alzheimer’s disease, a milestone that could allow treatment for the degenerative disease to begin at a much earlier stage than it does today.

Most patients today do not begin treatment until after significant deficits show up, making the prospect of early predictive tests highly attractive. If perfected, the tests could allow physicians to be on close watch for memory loss and other early signs of memory loss that presage the onset of Alzheimer’s.

Drugs currently approved for treating Alzheimer’s are limited to addressing its symptoms. The tests could also become more valuable if drugs treating the underlying biological mechanisms of the disease become available. In that case, prevention may become possible.

Genetic Markers

At the 2007 Alzheimer’s Association International Conference on Prevention of Dementia in Washington, a team of Norwegian researchers announced they had isolated some 1,200 genes that, taken together, can closely predict Alzheimer’s.

When researchers combined the genes and tested the blood of known Alzheimer’s patients, they found the genes could predict onset of the disease with 85% accuracy.

A second test containing just 96 genes predicted the disease with 80% accuracy, though presumably at a potentially lower cost than the more complex screen.

The tests are currently in large-scale trials with results expected next year, Anders Lönneborg, PhD, research director at DiaGenic ASA, the company pursuing the test, said at the International Conference on the Prevention of Dementia.

Testing for Proteins

Early detection could also get a boost from another blood test under investigation at a Belgian company. Researchers say they can use existing lab tests to predict which patients are at risk for developing dementia later.

Scientists identified two forms of amyloid protein circulating in the blood. Since the protein is known to be a marker for Alzheimer’s disease in the brain, finding abnormalities in blood levels could also wind up being a reliable early predictor of disease.

Early tests show that a blood test comparing the two amyloid proteins identifies most patients at risk for Alzheimer’s, said Geert DeMeyer, PhD, a biostatistician with Innogenetics, the firm hoping to market the test.

The test does not definitively tell who will develop the disease. “This is not a diagnostic test," DeMeyer said. "What it can do is predict what could happen to people down the road."

Brain Scans

Another research team says they can use a combination of magnetic resonance imaging (MRI) scans and positron emission tomography (PET imaging) to identify the earliest changes of the brain that are characteristic of mild cognitive impairment (MCI). MCI is marked by memory problems that aren't severe enough for dementia diagnosis.

MRIs, which provide detailed brain images, can already be used to help identify physical signs of cognitive impairment in the brain. Still, the accuracy is limited.

Researchers combined the MRI scans with PET imaging of blood flow in the brain in a small study of 30 people (half with MCI and half who without cognitive problems), to pinpoint patterns of changes in the brain researchers say provided diagnosis of mild cognitive impairment 100% of the time.

“In many individuals, they can be identified and measured even before the patient’s mental processes deteriorate to the point of clinical symptoms,” said Christos Davatzikos, PhD, a researcher at University of Pennsylvania in Philadelphia.

  • Alzheimer's can be elusive to spot in a loved one, especially in the early stages. How did you and your loved one's medical team determine it was Alzheimer's? What us your diagnostic journey? Tell us in WebMD's Alzheimer's Disease: Support Group message board.

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