An experimental test to detect minute differences in the brain caused by Alzheimer's disease works in the lab, Canadian researchers say.

Prof. Vassilios Papadopoulos, director of the McGill University Health Centre's Research Institute, and his co-authors published their findings about the test in Wednesday's issue of the Journal of Alzheimer's Disease.

Papadopoulos and his co-authors used a blood test to look for biochemical changes in the blood of 39 people with Alzheimer's disease, 40 healthy people of the same age, and another seven people with mild cognitive impairment — mild changes in memory and thinking abilities that can be noticed but don't compromise everyday activities and functioning.

"The biggest problem today we have for understanding the disease 

[and] for the treatment is that we don't know when this disease [starts] ... the critical steps of progression we don't even know," said Papadopoulos. 
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A test for Alzheimer's needs to measure the mechanism behind the disease, says Dr. Peter St. George-Hyslop. (Courtesy of University of Toronto)

The researchers found that by measuring levels of a brain hormone in the blood, they could detect Alzheimer's disease.

A quick, non-invasive test would allow doctors to tell if someone has cognitive problems, screen them earlier and see if they need a special program or protocol, Papadopoulos said.

Such a test remains elusive. Scientists are making progress in understanding the genetic causes of Alzheimer's, but the mechanism of how nerve cells are killed in the brain remains a mystery.

"To have a good test for Alzheimer's disease, you really need to be measuring the mechanism for the disease, and if you don't understand that then basically most times your test is not going to be an accurate reflection of what's going on," said Dr. Peter St. George-Hyslop, director of the Tanz Centre for Research in Neurodegenerative Diseases at the University of Toronto.

St. George-Hyslop has seen new tests proposed for Alzheimer's "probably a couple times a year over the last 10 years," but none have come to fruition. 

What is known is that tangles of proteins are found in brain cells killed off by Alzheimer's. But there is no effective treatment to stop that progression, nor is it possible to forecast accurately when symptoms will become incapacitating. 

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Vic Southon showed signs of Alzheimer's two years before doctors confirmed the diagnosis. (CBC)

That's vital information for family members like Judy Southon of Toronto. Southon saw warning signs in her husband, Vic, two years before doctors confirmed he had Alzheimer's.

"I would have planned," Southon said. "I would have looked at treatment. I may not have been receptive to all of them, but then my husband would have had the opportunity to be engaged also. So we could have had a joint discussion. We could have talked about it."

An early diagnostic test can't change the course of the disease, but it could help families to start making the home environment safer for their loved one during early stages of the disease when a caregiver is away, and to teach memory aids when the patient is still receptive, St. George-Hyslop said.

The research was funded by the U.S. National Institutes of Health and Samaritan Pharmaceuticals.

With files from CBC's Kelly Crowe