Key Takeaways
- A blood marker rose with CTE severity.
- Only 11 confirmed CTE cases were studied.
- The test is not validated for diagnosis.
A Diagnosis That Today Arrives Only After Death
For families of boxers, football players and soldiers, it is the cruelest feature of chronic traumatic encephalopathy: CTE can only be confirmed by examining the brain after death. In life, doctors are left guessing from symptoms that overlap with Alzheimer's disease and other brain disorders.
A study published in JAMA on November 13 offers an early clue that blood might one day help. Researchers at Washington University School of Medicine in St. Louis and UC San Francisco measured a tau protein fragment called eMTBR-tau243 — a marker the same team had already linked to tau buildup in Alzheimer's — in blood from 229 people, including samples studied after death.
One patient's blood stood out: very high marker levels, no Alzheimer's at autopsy — but advanced CTE. When the team tested blood from 11 people whose CTE was confirmed at autopsy, levels were higher than in healthy people and rose with the severity of the disease.
An Important Discovery, With Important Limits
This is a clue, not a test. Eleven confirmed CTE cases is a very small foundation. The marker could not reliably identify early-stage CTE, and because it also runs high in Alzheimer's — which often occurs alongside CTE — it cannot tell the two apart on its own. The researchers say plainly it has not been validated for diagnosing CTE, and larger studies are needed before any clinical use.
"This is not going to be a standalone biomarker," said co-senior author Chihiro Sato of WashU Medicine. "But if someone has a history of repeated head injury, tests negative for Alzheimer's, and this biomarker comes up, it might be CTE."
One more thing worth knowing: WashU has licensed the measurement technology to C2N Diagnostics, a startup in which the university and one of the senior authors hold equity — a disclosed interest readers should weigh alongside the findings.
The Twikup Take
For a disease that can only be confirmed after death, the possibility of detecting clues through a blood test is an exciting step forward. But excitement and proof are two different things. The science here is genuinely exciting — a living-person window into a disease that has only ever been confirmed in the morgue. Just keep the proportions right: 11 cases opened the door. Hundreds more will decide whether anything walks through it.
Health note: a high or low result on any tau blood test today says nothing definite about your own brain. Memory or mood changes after head injuries deserve a clinician's workup, not a single biomarker.
Image: Illustrative image.