Scientists identify 10 blood proteins linked to Alzheimer's disease

British scientists have identified a set of 10 proteins in the blood that they believe can someday be used to predict the onset of Alzheimer’s disease, according to a study published Tuesday.

The scientists, from King’s College London and the U.K. biotechnology company Proteome Sciences, hope the blood test could eventually be used to identify likely Alzheimer’s sufferers earlier, so that they can be entered into clinical trials for experimental drugs to slow the atrophying of the brain before the disease has progressed, the researchers said.

“What we want is to move earlier, to test on people who don’t currently have dementia,” said Simon Lovestone, a neuroscience professor at the University of Oxford’s Psychiatry Department and co-author of the study, which was published in Alzheimer’s & Dementia (PDF), the journal published by the Alzheimer’s Association.

Alzheimer’s disease is the most common form of dementia, affecting an estimated 5.2 million people in the U.S., the majority of them over the age of 65. It’s characterized by progressive memory loss, and in the later stages, Alzheimer’s sufferers lose the ability to have conversations or function normally, according to the Alzheimer’s Association, an advocacy group.

There are no cures for the disease, and while drug companies have tested hundreds of potential treatments over the past decade, clinical trials are “failing disastrously and expensively,” Lovestone said.

Because Alzheimer’s begins to affect the brain years before patients are diagnosed with it, he said clinical trials might be testing drugs on patients who are too far along in the disease process.

Current research on Alzheimer’s biomarkers involves examining the cerebrospinal fluid or using PET scans to test for atrophying of the brain, the study said. But Lovestone and his team wondered whether they’d be able to use a less invasive and more inexpensive method — a blood test — to earlier identify.

“Detecting AD [Alzheimer’s] at the earliest possible stage is vital to enable trials of disease modification agents and considerable efforts are being invested in the identification and replication of biomarkers for this purpose,” the authors wrote in the study.

Scientists had previously identified 26 different proteins in the blood that might serve as biomarkers for determining whether people develop Alzheimer’s.

In this study, the researchers used blood samples from more than 1,100 people culled from three different international studies, some who had Alzheimer’s, some who had “mild cognitive impairment” and some who had neither.

After identifying 16 out of the 26 previously discovered proteins as “strongly associated” with brain shrinkage, they ran a second set of tests in which 10 of those proteins predicted the progression from mild cognitive impairment to Alzheimer’s with 87 percent accuracy, they said. 

Lovestone said that while far more research and replication of these results need to be done, he is “cautiously excited to be at this point.”

James Pickett, head of research at the Alzheimer's Society, told Reuters the research "does not mean that a blood test for dementia is just around the corner.”

Still, as Lovestone said, “When we started off this research, we were setting out to show that a blood test was absolutely not possible. I think we’ve proved ourselves wrong on that point."