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Blood proteins may diagnose Alzheimer's

A simple test could one day help target early treatments.

What goes on in the brain can affect proteins in the blood. Credit: W. CRUM, DEMENTIA RESEARCH GROUP, T. BEDDOW/SPL

A survey of Alzheimer?s patients has identified some distinctive proteins in the blood that could be used to diagnose the disease more effectively. Earlier and more definitive diagnoses are wanted to help target treatments ? both existing and experimental.

More than 5 million North Americans currently have Alzheimer?s disease. It is estimated that about quarter of a million developing cases go undiagnosed every year.

Doctors can diagnose Alzheimer?s only by eliminating other possible causes of mental decline. There is no definitive test for the disease until a person dies, when surgeons can examine his or her brain tissue to look for the protein plaques and tangles that are the hallmark of the disease.

Researchers are trying to change that situation by finding biomarkers ? definitive biological signatures of the disease. Today, a team led by neuroscientist Tony Wyss-Coray of Stanford University School of Medicine in California reports in Nature Medicine1 the discovery of 18 proteins that together seem fairly diagnostic for the condition.

If the biomarkers are confirmed by more rigorous testing, they could result in a simple blood test by which doctors could diagnose the disease. Sufferers could then take medications to delay the effects of Alzheimer?s, plan to change their finances or living situation, or enroll in clinical trials to test potential new drugs.

The communicode

Wyss-Coray?s team examined proteins in 259 blood samples from people with and without Alzheimer?s disease. The researchers looked at 120 proteins that cells use to communicate with each other ? a set of proteins they dubbed the 'communicode'. The idea was that changes to such proteins in brain cells affected by Alzheimer?s might leach into the blood system.

?The idea was to look at factors in the blood that could tell us whether there is a disease process going on in the brain or not,? Wyss-Coray says.

A set of 18 of these communication proteins occurred at different levels in the blood of people with and without Alzheimer?s disease, they found. Researchers then looked at levels of these proteins in 20 patients whose Alzheimer?s or non-Alzheimer?s status had been determined by other doctors. The researchers did not know which samples related to which patients. The protein diagnosis agreed with the doctors? assessments for 18 of the 20; in one case, doctors made an Alzheimer?s diagnosis that the proteins did not flag, and in another the proteins indicated Alzheimer?s where the doctors did not agree.

The work was supported by two Alzheimer?s foundations, the US National Institute on Aging and a biotechnology company in Redwood City, California, called Satoris. Wyss-Coray is a paid consultant for Satoris and a founder of the company, which also employs two more of the study?s 25 authors.

Best observation

Other scientists are investigating alternative possible diagnostics for Alzheimer?s. Some are using high-powered imaging studies to examine people?s brains to look for characteristic plaques and tangles while they are still alive. Others have found that proteins from these plaques can be detected in the cerebrospinal fluid, which surrounds the spinal cord and can be accessed through a spinal tap.

But, Wyss-Coray says, many studies are beginning to support the idea that a biomarker outside the brain could allow earlier and easier diagnosis. Examining blood is easier and potentially cheaper than using spinal taps or imaging.

Although there is no cure for Alzheimer?s, Wyss-Coray says it could still help patients to know they are affected.


  1. [Author]Sandip R[/Author]., et al. [Journal Title]Nature Medicine[/Journal Title] advanced online publication DOI: 10.1038/nm1653

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Check Hayden, E. Blood proteins may diagnose Alzheimer's. Nature (2007).

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