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A blood test for Alzheimer's disease may soon be available

Dominika Osmolska Psy.D.'s picture

A simple blood test for Alzheimer’s disease is just around the corner, a team of Australian researchers announced Wednesday. The question is, would you want to be tested if given the opportunity? As the second most-feared disease after cancer, it brings many a patient knocking on his or her doctor’s door with worries and questions about cognitive loss.

Researchers at the Commonwealth Scientific and Industrial Research Organization in Perth, Australia, say an experimental screening tool proved about 85% accurate at determining the amount of Alzheimer's-associated plaque in people's brains.

If the findings can be replicated in large numbers of people, the screen might one day help indicate whether a person is in the early stages of, or at risk of developing, Alzheimer's, says researcher Samantha Burnham. The test may also help doctors make further diagnostic decisions for patients who demonstrate cognitive loss, such as more expensive imaging scans.

Currently, Alzheimer’s disease can only be definitively diagnosed post mortem, upon discovery of the telltale deposits of beta amyloid plaque in brain tissue. However, the diagnosis is often made in living patients through a complex procedure involving numerous steps, including brain imaging through CT and fMRI scans, neuropsychological assessment, mental status exams, as well as physical and neurological exams.

Beta amyloid plaque begins to build up in the brain seven to ten years before cognitive decline becomes noticeable.

A spinal tap, which obtains a sample of the cerebrospinal fluid, can also be performed – a procedure which can yield a lot of data indicative of the probability of Alzheimer’s. But a spinal tap is an invasive and very painful procedure most people would rather avoid.

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The new blood test, which spots nine proteins whose levels appear to correlate with amyloid levels in the brain, is one of hundreds in development. What makes this one stand out is that it was validated against PET scans of the brain in a relatively large study.

To develop the noninvasive blood test, Burnham and colleagues used blood samples from 273 people participating in a large-scale study looking for new biomarkers for dementia.

First, they identified nine proteins that correlated with the amount of amyloid deposited in the brain.

A cutoff level was set for what was considered high.

When researchers used the nine-marker blood test on these same participants, they found that it separated healthy people from those with mild cognitive impairment or Alzheimer's as verified by their brain scans. The test correctly identified 83 percent of people with high amyloid levels and correctly ruled out 85 percent of people without this condition. “That’s pretty accurate when you consider that brain scans are only about 90% accurate," Burnham says.

Alzheimer’s disease is the most common type of dementia and approximately 5.4 million people are thought to suffer from the disease in the U.S.

About 35 million people are thought to suffer from the disease across the globe. As the population grows older still, the worldwide total is predicted to triple by the year 2050.