Study links blood biomarker to advanced CTE, but diagnostic test remains unproven

Researchers have identified a blood biomarker associated with advanced chronic traumatic encephalopathy, offering a possible route toward detecting the brain disease in living people. The finding concerns a condition linked to repeated head impacts, a major issue for contact sports including rugby and American football. It does not mean a validated CTE blood test is now available.

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According to Washington University School of Medicine in St. Louis, the research was published in JAMA on November 13. Scientists studied eMTBR-tau243, a fragment of the tau protein already investigated in Alzheimer's disease. Both conditions involve abnormal tau accumulating in the brain, so the researchers examined whether the marker could signal diseases beyond Alzheimer's rather than being specific to that condition.

The paper reports blood results from 11 people whose CTE was confirmed after death: five with stage I disease, two with stage III and four with stage IV. Biomarker levels increased across those stages and were higher overall than in the control group. However, the researchers could not reliably identify early-stage CTE, an important limit on the finding's potential use for screening.

The discovery emerged from a wider investigation of brain diseases, WashU reported. One participant had an unexpectedly high biomarker reading despite having no Alzheimer's pathology; examination of the records showed advanced CTE. Researchers then investigated the additional CTE blood samples. The wider study involved 229 participants, but that total should not be confused with the much smaller group supplying blood samples linked to confirmed CTE.

The authors stressed that interpretation would require clinical information and other biomarkers. Elevated readings can occur in several conditions, and Alzheimer's pathology can coexist with CTE. Their paper does not establish the accuracy of using this marker to diagnose CTE during life. It also identifies limitations involving scarce samples, differences between participant groups and the interval between sample collection and autopsy.

For athletes and former players, the immediate result is a research lead rather than a new clinical diagnosis. Larger, independent studies following participants over time are needed. WashU said successful validation could eventually help monitor people at risk and support trials of potential treatments.