A new imaging molecule may help to identify Alzheimer's disease, researchers say.

Currently, the only way to tell whether someone has the brain disorder is to remove some brain tissue or perform an autopsy.

Brain PET scans from a healthy volunteer (top), a subject with mild cognitive impairment (middle) and a subject with Alzheimer's disease (bottom). Red and yellow areas show the new chemical marker FDDNP binding to abnormal brain proteins or "plaques and tangles."
(Courtesy UCLA)

The disease slowly leads to memory impairment, behavioural changes and dementia, affecting how people understand, think, remember and communicate.

Doctors at the University of California, Los Angeles, say they have found a better way using chemical tracers that can be detected with a PET scan.

"The study suggests that we may now have a new diagnostic tool for detecting pre-Alzheimer’s conditions to help us identify those at risk, perhaps years before symptoms become obvious," said Dr. Gary Small, a professor of aging at UCLA who led the study in Thursday's New England Journal of Medicine.

The chemical, called FDDNP, attaches to plaques and tangles found in the abnormal deposits of people with Alzheimer's disease.

In the experiment, researchers looked at 83 people aged 49 to 84. Cognitive tests suggested 25 of the participants had Alzheimer's, 28 had memory problems from mild cognitive impairment and the rest were normal controls.

Distinct differences found

Distinct differences were found in the PET images between people with normal brain aging, Alzheimer's disease and mild cognitive impairment.

The scans were 98 per cent accurate at distinguishing between Alzheimer's and mild cognitive impairment, the researchers said.

In comparison, a PET scan that measured sugar metabolism in the brain showed 87 per cent accuracy, and MRI scans were 62 per cent accurate.

The pattern of FDDNP in the brain of people with Alzheimer's matched what doctors see when the diagnosis is confirmed at autopsy.

"This imaging technology may also allow us to test novel drug therapies and manage disease progression over time, possibly protecting the brain before damage occurs," said Small.

Small and four of the other 15 authors of the study reported they had a financial interest in FDDNP. A test based on it could be on the market in three years, he said.

Alzheimer's is the most common form of dementia and affects one in 20 Canadians over 65 — about 290,000. The number rises to one in four in those over 85.