Not knowing whether those memory lapses are just that, or the beginning of Alzheimer’s disease, is one of the most distressing aspects of the disease, say researchers from the Stanford University School of Medicine. They say they have developed a blood test which may eventually tell you two to six years before the onset of Alzheimer’s disease starts (before symptoms appear).
There are some proteins in blood plasma which cells utilize to pass messages to one another – this blood test identifies changes in these proteins. The scientists have found a link between a change in the cells’ dialog and alterations in the brain that comes with Alzheimer’s. The researchers explain the blood test indicated who had Alzheimer’s disease with 90% agreement with clinical diagnoses. The test could predict onset of the disease 2 to 6 years before symptoms started to become evident.
Senior author, Tony Wyss-Coray, wrote “Just as a psychiatrist can conclude a lot of things by listening to the words of a patient, so by ‘listening’ to different proteins we are measuring whether something is going wrong in the cells. It’s not that the cells are using new words when something goes wrong. It’s just that some words are much stronger and some are much weaker; the chatter has a different tone.”
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Lennart Mucke, MD, director and senior investigator, Gladstone Institute of Neurological Disease, University of California-San Francisco, who did not take part in the study, said “I really think it has enormous potential. Most researchers in this field agree that there is an urgent need for better lab tests for Alzheimer’s disease, and this study has addressed this need admirably.”
The researchers explained that listening to cells’ messages may also lead to discoveries about other disorders.
Alzheimer’s diagnosis today is reached by a process of elimination – the patient is tested for stroke, tumors, alcoholism and other possible causes of memory loss and cognitive decline. These conditions are eliminated until all that is left is Alzheimer’s. Alzheimer’s is the most common cause of dementia. Currently, the only way diagnosis can be confirmed is by carrying out an autopsy after the patient has died.
There are currently over 5 million Americans with Alzheimer’s disease, according to the Alzheimer’s Association.
The idea of a blood-test was born when Wyss-Coray and Sandip Ray worked together to measure levels of 120 different proteins that cells use to communicate. They wanted to find out whether any of them could be indicators for Alzheimer’s.
Sandip Ray compared blood samples of five Alzheimer’s patients with five samples from healthy people (who did not have the disease). He noticed that there were significant difference in the levels of some proteins which are used for communication between the two groups.
Markus Britschgi, PhD, a postdoctoral scholar in Wyss-Coray’s lab, said “This study made me realize that we should get away from this image of a brain isolated from the body. The brain is part of the body and so it’s connected in one huge network.”
Britschgi managed to obtain 258 archived blood samples from the USA, Sweden, Italy, and Poland, of individuals who had symptoms ranging from nothing abnormal to mild cognitive impairment to advanced Alzheimer’s. They tested 120 communication proteins, checking to see whether there were any differences in blood samples of Alzheimer’s patients and individuals without the disease. They eventually managed to identify an Alzheimer’s-specific pattern with just 18 proteins. The blood test was 90% accurate with 92 individuals who ranged from no symptoms at all to full dementia.
They then tried to predict the development of Alzheimer’s with 47 individuals who had mild cognitive impairment and had been monitored from 2 to 6 years. The blood test had been carried out on these individuals several years earlier. The blood test flagged 91% of the people who developed Alzheimer’s by the end of the monitoring period (as diagnosed by conventional methods).
Britschgi said “Already we have people approaching us at meetings asking if they can give us a vial of their grandfather’s blood for testing.”
Even though it appears that this blood test seems to be able to predict Alzheimer’s disease, as well as diagnosing it, the scientists stress that tests need to be carried out in other labs to confirm this.
Wyss-Coray said “Our hypothesis is that there is something wrong with the production of certain blood cells, which may be needed to clear that stuff that accumulates in the brain in Alzheimer’s disease. That makes a lot of sense, and it is very exciting to think of immune cells and molecules interacting with the brain.”
Written by: Christian Nordqvist