CTE blood-marker study offers early lead for contact-sport research

Researchers at Washington University School of Medicine in St. Louis have identified a possible blood marker for advanced chronic traumatic encephalopathy, a finding with potential relevance for former contact-sport athletes. The university's announcement said the work was published in JAMA on November 13, but stressed that the test has not been validated for diagnosing CTE.

The researchers examined blood from 11 people whose CTE was confirmed after death. Levels of the protein fragment eMTBR-tau243 were higher than in healthy participants and increased with disease severity. However, the test could not reliably identify early-stage CTE. The university said larger studies would be needed before clinical use.

An important limitation is that the marker is also elevated in Alzheimer's disease. According to the university, it cannot distinguish the two conditions on its own. If confirmed, the findings could support monitoring of people at risk and trials of treatments targeting harmful tau protein.

Independent scrutiny also underlined the uncertainty. The Associated Press reported that Northwestern University neuropathologist Dr. Rudolph Castellani, who was not involved in the research, regarded the finding as interesting but very preliminary. He said much larger studies were necessary to establish whether the connection holds. AP also noted that abnormal tau occurs in several brain diseases, which can overlap in older adults and make it difficult to determine its role in a particular condition.

For sport, the wider issue extends beyond diagnosed concussions. The US Centers for Disease Control and Prevention says repeated head impacts can occur without immediate symptoms, including during sporting collisions. Its guidance associates CTE with long-term exposure to repeated impacts, while noting that strong evidence does not show that occasional blows or one or more concussions alone lead to CTE. Researchers still need to establish why some people with prolonged exposure develop the condition and others do not.

The CDC also cautions that thinking, mood or behavioural problems do not establish that someone has CTE. Confirmation currently requires examination of the brain after death. The new research therefore remains a possible route towards future diagnosis, not an available test that can resolve an individual athlete's concerns today.