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• Posted April 4, 2025

New Blood Test Can Diagnose, Track Alzheimer’s Disease

An experimental blood test for Alzheimer’s disease not only can aid in its diagnosis but also indicate how far the brain condition has progressed, a new study says.

The test tracks levels of a protein called MTBR-tau243, which is linked to toxic tau tangles that build up in the brain as part of Alzheimer’s disease, researchers said in the journal Nature Medicine.

Using the test among a group of people in cognitive decline, researchers were able to distinguish between early- or later-stage Alzheimer’s disease, the study said.

Researchers also were able to separate Alzheimer’s patients from folks whose brain decline was being caused by something other than Alzheimer’s, results show.

“This blood test clearly identifies Alzheimer’s tau tangles, which is our best biomarker measure of Alzheimer’s symptoms and dementia,” co-senior author Dr. Randall Bateman, a professor of neurology at the Washington University School of Medicine in St. Louis, said in a news release.

“In clinical practice right now, we don’t have easy or accessible measures of Alzheimer’s tangles and dementia, and so a tangle blood test like this can provide a much better indication if the symptoms are due to Alzheimer’s and may also help doctors decide which treatments are best for their patients,” Bateman added.

Toxic accumulation of amyloid beta and tau proteins are two of the hallmarks of Alzheimer’s, researchers said in background notes.

Amyloid beta first starts forming plaques in the brain, and that’s followed by the development of tau tangles years later, researchers said. The first signs of brain decline emerge around the time tau tangles become detectable, and symptoms worsen as the tangles spread.

Brain scans are the gold standard for determining how far Alzheimer’s has progressed, but they are expensive, time-consuming and frequently not available outside major research centers, researchers said.

Bateman and his colleagues are working on blood tests for Alzheimer’s that could provide a more accessible alternative to brain scans. They’ve already developed two blood tests in clinical use that can track the buildup of amyloid plaques in the brain, and now are looking for a way to use blood to detect tau buildup.

In a previous study, they showed that MTBR-tau243 levels in spinal fluid closely correlate with tau tangles in the brain. However, a blood sample is much easier to collect, so they extended their analysis to blood.

Researchers developed the test based on blood data from 108 U.S. and 55 Swedish patients, and then checked whether it was accurate using another group of 739 people.

Patients in the study represented a range that included all but the most severe Alzheimer’s disease, researchers said. They ran from a presymptomatic stage with elevated amyloid levels through the development of mild cognitive impairment and, finally, full-blown Alzheimer’s dementia.

People with healthy brains and cognitive problems caused by diseases other than Alzheimer’s also were included, to see whether the test could distinguish them from Alzheimer’s patients.

Results showed that blood levels of MTBR-tau243 reflected the amount of tau tangles in a person’s brain with 92% accuracy.

MTBR-tau243 levels were significantly higher in people with mild cognitive impairment, and up to 200 times higher for those who’d developed dementia, researchers found.

However, the protein’s levels remained normal in people without symptoms of cognitive decline, even if they had started to develop amyloid plaques, researchers said. They also were normal in people with cognitive problems caused by something other than Alzheimer’s.

These blood tests could be used to help steer Alzheimer’s patients to upcoming drugs that one day will target tau proteins or other aspects of the brain disease, researchers said.

“We’re about to enter the era of personalized medicine for Alzheimer’s disease,” co-lead researcher Kanta Horie, a research associate professor of neurology at the University of Washington in St. Louis, said in a news release.

“For early stages with low tau tangles, anti-amyloid therapies could be more efficacious than in late stages,” he explained. “But after the onset of dementia with high tau tangles, anti-tau therapy or one of the many other experimental approaches may be more effective. Once we have a clinically available blood test for staging, plus treatments that work at different stages of the disease, doctors will be able to optimize their treatment plans for the specific needs of each patient.”

More information

The National Institute on Aging has more about brain changes during Alzheimer’s disease.

SOURCE: Washington University at St. Louis, news release, March 31, 2025