Study tested stored blood from 11 people classified as having CTE

Doctors trying to determine whether a patient has chronic traumatic encephalopathy currently have to work from symptoms such as mood swings and memory loss, because other diseases cause similar symptoms and a CTE diagnosis can only be confirmed by examining the brain after death. The JAMA finding raises the possibility that a blood measurement could one day help separate CTE from those lookalike conditions in football players and others who have suffered repeated blows to the head.

The clue involves tau, a protein that normally supports neurons but becomes abnormal in Alzheimer’s disease, tangling inside nerve cells. Researchers at Washington University in St. Louis were using autopsy samples to study a tau fragment called eMTBR-tau243 that may help track those tangles when they found something unusual: a patient with high levels of that biomarker even though records showed the person didn’t have Alzheimer’s but advanced CTE instead.

The researchers turned to a larger collection of autopsied brain and other samples, and eventually tested blood stored from 11 people who had been classified as having CTE. Compared to healthy people, levels of eMTBR-tau243 were higher in those with advanced CTE, said study coauthor Chihiro Sato, a WashU assistant neurology professor. That biomarker couldn’t reliably identify early-stage CTE.

Sato, who studies such tauopathies, also stressed much more research is needed. Abnormal tau is found in several brain diseases, many of which can overlap in older adults, adding to the difficulty in teasing apart its role in any one disease, including CTE.

An outside researcher urged caution. “It is an interesting but very preliminary finding, requiring far larger studies to see if there is a real connection,” said Dr. Rudolph Castellani, a neuropathologist at Northwestern University who wasn’t involved with the research.

The findings were published late Friday by the medical journal JAMA and presented at a scientific meeting in Japan.