Blood test can detect ‘toxic’ proteins years before Alzheimer’s symptoms – study

A blood test could detect a toxic protein years before symptoms of Alzheimer’s disease appear, a new study has found.

Currently, patients tend to be diagnosed with Alzheimer’s disease only after showing well-known signs of the disease, such as memory loss.

However, at this stage, the best treatment options simply slow the progression of symptoms, experts say.

But research suggests that the seeds of the disease are planted many years before the symptoms that make diagnosis possible.

These seeds are called amyloid beta proteins which misfold and clump together and form what are called oligomers.

Over time, the toxic oligomers are thought to develop into Alzheimer’s – although scientists are still trying to understand the process by which this occurs.

Researchers at the University of Washington (UW) have developed a laboratory test capable of measuring the levels of beta-amyloid oligomers in blood samples.

The study suggests that their test – known by the acronym SOBA – could detect oligomers in the blood of patients with Alzheimer’s disease, but not in most members of a healthy test group who had no signs of cognitive impairment at the time the blood samples were taken.

However, according to the study, the test was able to detect oligomers in the blood of 11 people in the non-Alzheimer’s group.

When the researchers reviewed the follow-up records of 10 of these people, all were diagnosed years later with mild cognitive impairment or brain pathology compatible with Alzheimer’s disease.

Essentially, for those 10 people, SOBA had detected the toxic oligomers before symptoms appeared, the scientists said.

Lead author Valerie Daggett, a UW professor of bioengineering and faculty member at the UW Molecular Engineering & Sciences Institute, said, “We believe SOBA could help identify people at risk or incubate disease, as well as serve as a readout of therapeutic efficacy to aid in the development of early treatments for Alzheimer’s disease.

She added: “What clinicians and researchers have wanted is a reliable diagnostic test for Alzheimer’s disease – and not just a test that confirms a diagnosis of Alzheimer’s disease, but one that can also detect signs of illness before cognitive impairment occurs.

“It’s important for the health of individuals and for all research into how toxic amyloid-beta oligomers go on and cause the damage they do.”

“What we show here is that SOBA can be the basis for such a test.”

SOBA, which stands for Soluble Oligomer Binding Assay, exploits a unique property of toxic oligomers, according to the researchers.

When misfolded beta-amyloid proteins begin to clump together into oligomers, they form a structure known as an alpha sheet — which tends to stick to other alpha sheets, research shows.

The SOBA test features a synthetic alpha sheet that can bind to those detected in blood samples.

The test then uses standard methods to confirm that the oligomers attached to the test surface are made of beta-amyloid proteins.

The team tested SOBA on blood samples from 310 research subjects who had previously made their blood samples and some of their medical records available for Alzheimer’s disease research.

They detected oligomers in the blood of people with mild cognitive impairment and moderate to severe Alzheimer’s disease.

The results are published in the Proceedings of the National Academy of Sciences.

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