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

Currently patients tend to receive a diagnosis of Alzheimer’s only after they show well-known signs of the disease, such as memory loss.

However, at that point the best treatment options simply slow further progression of symptoms, experts say.

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

We believe that SOBA could aid in identifying individuals at risk or incubating the disease, as well as serve as a readout of therapeutic efficacy to aid in development of early treatments for Alzheimer’s disease

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

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

Researchers at the University of Washington (UW) developed a laboratory test that can measure levels of amyloid beta oligomers in blood samples.

The study suggests their test — known by the acronym SOBA — could detect oligomers in the blood of patients with Alzheimer’s, but not in most members of a healthy trial group who showed 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 from the non-Alzheimer’s group.

When researchers looked at follow-up records for 10 of these people, all of them were diagnosed years later with mild cognitive impairment or brain pathology consistent with Alzheimer’s disease.

Essentially, for these 10 people, SOBA had detected the toxic oligomers before symptoms surfaced, the scientists say.

Senior author Valerie Daggett, a UW professor of bioengineering and faculty member in the UW Molecular Engineering & Sciences Institute, said: “We believe that SOBA could aid in identifying individuals at risk or incubating the disease, as well as serve as a readout of therapeutic efficacy to aid in 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 an assay that confirms a diagnosis of Alzheimer’s, but one that can also detect signs of the disease before cognitive impairment happens.

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

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

SOBA, which stands for soluble oligomer binding assay, exploits a unique property of the toxic oligomers, researchers say.

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

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 up of amyloid beta 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 research.

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

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