Blood Test Spots Signs of Advanced CTE in Early Study of 11 Autopsy-Confirmed Cases

A blood test that tracks a toxic protein tied to Alzheimer’s disease also picked up signs of advanced chronic traumatic encephalopathy, the brain disease linked to repeated blows to the head, in a small study published Friday, Nov. 13, 2026, in the journal JAMA.^[1] The marker could not reliably identify early-stage CTE, and researchers said much larger studies are needed before a CTE blood test could be used in patients.^[1]

Related: Alzheimer’s genetic study of 2.8 million people finds 48 new risk regions.

What the study found

The research, led by Washington University School of Medicine in St. Louis, measured a tau protein fragment called eMTBR-tau243. The same team had previously shown that blood levels of the fragment reflect the buildup of tau clumps in the brains of people with Alzheimer’s disease.^[1]

Working with collaborators at UC San Francisco, the researchers tested samples from more than 80 people whose brain diseases were confirmed at autopsy, along with healthy volunteers. Levels were very high in Alzheimer’s and low in diseases where only one form of tau builds up. One person stood out with a high level despite no signs of Alzheimer’s; autopsy records showed advanced CTE instead.^[1]

The team then tested stored blood from 11 people whose CTE had been confirmed at autopsy.^[2] Their levels were higher than in healthy people and rose with the severity of the disease. The test separated advanced CTE from healthy people with high accuracy.^[1] The fragment was also elevated in some inherited forms of frontotemporal dementia.^[1]

Why a blood test matters

CTE can now be confirmed only by examining the brain after death. Doctors look at symptoms such as mood swings and memory loss, but other diseases cause similar problems.^[2]

Co-senior author Kanta Horie, a research associate professor of neurology at WashU Medicine, said drug companies are developing possible CTE treatments but have no biomarkers to identify the disease or quickly see whether a treatment works.^[1] If larger studies confirm the results, a blood test could be used to monitor people at risk, such as former football players, boxers and combat veterans, and to support drug trials.^[1]

Limits of the research

The CTE group was small, and the marker did not reliably catch early-stage disease. Levels in CTE were much lower than in Alzheimer’s, and because Alzheimer’s often occurs alongside CTE, the marker alone cannot tell the two apart.^[1] “This is not going to be a standalone biomarker,” said co-senior author Chihiro Sato, an assistant professor of neurology at WashU Medicine.^[1]

Abnormal tau appears in several brain diseases that often overlap in older adults, which makes its role in any single disease hard to isolate.^[2] Dr. Rudolph Castellani, a Northwestern University neuropathologist who was not involved in the research, called the finding interesting but very preliminary and said far larger studies are needed to show a real connection.^[2]

What happens next

WashU has licensed the technology for measuring eMTBR-tau243 in blood to C2N Diagnostics, a WashU startup that also developed an FDA-cleared blood test to help diagnose Alzheimer’s disease. The test has not been validated for diagnosing CTE.^[1] The findings were also presented at a scientific meeting in Japan.^[2]

For more brain research coverage, see Mass General Brigham’s $41.2 million Alzheimer’s prevention trial, a study linking high-dose flu shots to lower Alzheimer’s risk and the Health and Science hub.

Sources

1. WashU Medicine: Progress toward a blood test for CTE
2. NBC Boston (Associated Press): Preliminary study finds a clue in the quest to help diagnose CTE in the living

About the reporter: Theo Lin is an AI reporter covering AI news, technology and science for The Boston Report. This article was produced with AI under our editorial policy. Read our AI and media disclosure.