Researchers may have uncovered a way to detect chronic traumatic encephalopathy (CTE) in living individuals with a blood test that detects plasma exosomal tau.
The preliminary results were published in the Journal of Alzheimer’s Disease.
A definitive diagnosis of CTE has previously only been attainable through autopsy. As public concern over the degenerative brain disease has grown, so has the search for objective biomarkers that can be used to diagnose and monitor CTE during life.
In this study, investigators from Boston University and the University of Washington, along with Exosome Sciences, Inc. developed the TauSome blood test to measure exosomal tau in plasma. Exosomes have previously been shown to reflect the content of the cell of origin, and readily cross the blood-brain barrier, making them a good potential marker of brain tau pathology.
In total, 78 former National Football League (NFL) players and 16 healthy controls were included in the study. The NFL players (male, age 40-69) had played a minimum of 12 years of organized tackle football, 2 years of play in the NFL at positions known to be subject to extensive head impacts, and had self-reported cognitive, behavioral, and mood symptoms for a minimum of 6 months prior to study participation. Controls were male, aged 40-69, with at least 4 years of participation in an organized, non-contact sport, with at least 2 years at the college level or beyond with no history of concussion or other traumatic brain injury.
Blood draws were conducted at Boston University Medical Center and processed by Exosome Sciences, Inc. Participants also underwent a battery of neuropsychological tests and completed self-report measures of mood and behavior.
Compared to controls, the NFL group had significantly higher levels of plasma exosomal tau (P<0.0001). This remained significant after controlling for age and body mass index (P<0.0001). Among the NFL group, plasma exosomal tau levels were significantly correlated with tests of memory and psychomotor speed, including the WAIS-R Digit Symbol test and the NAB List Learning test, with high levels associated with worse test scores. Exosomal tau levels were not significantly associated with measures of mood or behavior. Exosomal tau levels showed excellent sensitivity (82%), specificity (100%), and positive predictive value (100%) for discriminating between groups (c-statistic = 0.97, 95% CI = 0.94–1.00). This suggests that the method of exosome isolation yielded brain-derived exosomes, reflecting tau derived from brain cells.
Still, the researchers cannot be completely confident that the isolated exosomes were from the brain and if the p-tau measured in the test is the same form of abnormal tau found in CTE. Additional limitations include the small sample size and the lack of any other possible biomarker of CTE.
“We are extremely pleased that our initial study data has been published and we appreciate forthcoming opportunities to further advance our TauSome™ biomarker as a non-invasive solution to detect and monitor CTE in living individuals,” Jim Joyce, founder of Exosome Sciences and Chairman and CEO of Aethlon Medical, said in a statement.
Additional studies, including a 7-year, multisite study are already planned to continue to examine TauSome as a viable test to detect CTE and monitor its progression in the living.