Quirks & Quarks

Would you take this new blood test that can screen for Alzheimer's?

This new blood test could revolutionize how we screen for Alzheimer's

A new blood test could that can detect Alzheimer's years before the disease symptoms appear could revolutionize the screening process for a degenerative disease that could affect nearly a million people in Canada by the year 2031. 

The need to track and monitor the disease has created a huge demand for better testing and eventual treatment or cure. The problem with current tests, like PET (positron emission topography) scans and CSF (cerebrospinal fluid) samples is that they are expensive and invasive.

The new blood test

Now a team of researchers from Japan and Australia have developed a simple blood test for Alzheimer's disease that they hope will transform how the condition is studied and tracked. The biomarker-based blood test is accurate, scalable, and cheaper than current tests for the disease. The biomarkers are small molecules that shed into the blood, which can be detected in exceedingly low concentrations with high-tech devices like the one developed by the Japanese team led by Dr. Katsuhiko Yanagisawa

The accuracy of this test is greater than 90 percent as judged against the current standards.- Dr. Colin Masters, University of Melbourne

"The accuracy of this test is greater than 90 per cent as judged against the current standards. But it's so sensitive and specific that we believe that it may prove to be even better," Dr. Colin Masters told Quirks & Quarks host Bob McDonald.

The biomarker they are detecting is a ratio between two proteins — Aβ40 and Aβ42 — these two small proteins are broken down products of a protein called APP (amyloid precursor protein). APP is normally split as part of the cell's day-to-day recycling of proteins, but, for reasons not understood, the brain can process APP to produce the toxic Aβ42 small fragment. And it's the Aβ42 levels that worry Masters from the University of Melbourne.

"It's a highly aggregating protein that takes many years to build up in the brain. What happens is you get older is that the clearance mechanisms in the brain fail by 10 or 15 per cent. And slowly but surely over a 30-year period this protein builds up in the brain and causes extensive degeneration in the synapses. And that's the whole basis of Alzheimer's disease," he said.

(AFP/Getty Images)

The detection of such tiny amounts of circulating Aβ40 and Aβ42 has not been easy. Dr. Masters' Japanese colleagues have developed a device based on a technique called co-immunoprecipitation and mass spectroscopy to detect the ratio of the proteins in the blood. 

The reason why it has taken so long to develop an easy and effective blood test for Alzheimer's is the levels circulating in the blood are in near undetectable amounts. And, as the proteins start to accumulate in the brain the levels in the blood drop making the test for reduced levels even more difficult. Masters said the biomarker test they have developed has shown exceptional results. 

"We've monitored many individuals over a long period of time and we have a very clear idea now of what's normal and what's abnormal and it's just possible that this blood test may be supersensitive at the lower levels when people are moving from the normal range into the abnormal range."

Importance of testing early

The exceptional specificity and accuracy of the newly developed test can detect the markers for Alzheimer's up to 15 years before the symptoms are even present. The power of being able to detect this biomarker early could revolutionize how clinical trials are done and how the disease is monitored in patients. It will provide scientists with a way to determine if experimental early intervention techniques are working. If the Aβ ratio goes up, then the treatment is working even before someone starts to show cognitive decline. Not only that, a test will allow someone to determine how fast the disease is progressing after symptoms start to show. This may allow people suffering from the disease a little more clarity in how to plan for a future where their memory is taken from them. 

Who wants to know

I would wait until there's clear evidence of a therapeutic intervention.- Dr. Colin Masters, University of Melbourne

For a disease that has no known treatment or cure, a lot of people may simply not want to take the test. Even Dr. Masters says as it stands right now, he has no desire to test himself. "Personally I wouldn't have the test right now because even though I am in my early 70s. I would wait until there's clear evidence of a therapeutic intervention. It may be shown for example that some forms of environmental modulation of lifestyle, for example diet, sleep, exercise and so on, can slow this process down a little bit. If that data can be confirmed then obviously I would want to do the blood test myself and then take appropriate environmental modifications of my lifestyle at this point."

Paper in the journal Nature