Researchers at Washington University School of Medicine have identified a blood biomarker, a protein fragment known as eMTBR-tau243, that appears in patients with advanced chronic traumatic encephalopathy (CTE).
The findings, published November 13, 2026, in the journal JAMA, suggest a potential path toward diagnosing the degenerative brain condition in living patients.
The discovery of eMTBR-tau243, a tau protein fragment, provides a new tool that researchers believe could eventually help monitor individuals at high risk for the disease.
“We are potentially opening a new door for diagnosing and treating CTE in living patients,” said Kanta Horie, the study’s co-senior author. Horie presented these findings at a scientific meeting in Japan.
Horie and co-author Chihiro Sato, a WashU assistant neurology professor, initially stumbled upon a hint of this connection while using autopsy samples to study tau fragments. They identified a patient with high levels of the biomarker who did not have Alzheimer’s but instead had advanced CTE.
To further investigate, the team turned to a larger collection of autopsied brain and other samples, eventually testing blood stored from 11 people who had been classified as having CTE.
However, the researchers said that the biomarker could not reliably identify CTE in its early stages. Because the protein is also elevated in Alzheimer’s disease, which often occurs alongside CTE, the biomarker alone cannot distinguish the two conditions.
“This is not going to be a standalone biomarker,” Sato said. “But if someone has a history of repeated head injury, tests negative for Alzheimer’s and this biomarker comes up, it might be CTE.” She also emphasized that much more research is required.
CTE remains a major focus of concern across science and sport. Research involving almost 400 deceased National Football League (NFL) players who donated their brains to science revealed that 93.5% of them showed evidence of CTE.
A total exceeding 350 NFL athletes have received a post-mortem CTE diagnosis, a list that features Hall of Fame center Mike Webster, Junior Seau—who participated in two Super Bowls throughout his 20-year career—and former MVP Frank Gifford, who later became a well-known broadcaster. Boxer Ricky Hatton had a mild CTE diagnosis after his death, and living former rugby players diagnosed with Traumatic Encephalopathy Syndrome continue legal action.
While the findings offer a new direction for diagnostics, the test has not yet been validated for clinical use. Abnormal tau is found in several brain diseases, many of which can overlap in older adults, which adds difficulty in isolating its role in any single disease.
WashU has licensed the technology to measure eMTBR-tau243 in blood. Should subsequent extensive research verify these results, medical professionals might employ this blood test to track individuals prone to CTE—including combat veterans, boxers, and retired football players—while facilitating clinical trials for medications aimed at the damaging brain protein. Readers concerned about neurological symptoms should consult with qualified medical professionals to discuss their health history and appropriate diagnostic steps.
Reporting for this story was provided by AP Sports Writers Jim Vertuno, Aaron Beard, Tim Reynolds, Larry Lage, and Beth Harris. Funding for health and science reporting at The Associated Press is provided by private foundations and the AP Fund for Journalism.