Biomarkers Evaluated for Subconcussive Head Trauma

Repetitive subconcussive head trauma is a consequence of participation in contact sports and may be linked to neurodegenerative diseases. The degree of neurological injury caused by subconcussive head trauma is not easily detectible, and this injury does not induce readily identifiable clinical signs or symptoms.

The accumulation of subconcussive head impacts over the course of a football season has been linked to neurophysiological and neuropsychological changes in athletes, and the accumulation of subconcussive head impacts over a long career has been suggested as a cause of severe neurodegenerative diseases such as Alzheimer's disease and chronic traumatic encephalopathy (CTE).

Scientists at the Texas Christian University (Fort Worth, TX, USA) and their colleagues obtained blood samples from thirty-five National Collegiate Athletic Association (NCAA) football players on seven different days, beginning before fall camp commenced and ending three weeks after the competitive football season had finished. The investigators wanted to examine fluctuations in plasma concentrations of tau and serum concentrations of neurofilament light polypeptide (NF-L) over the course of the entire football season, during which the number and magnitude of head impacts varied.

After blood collection, subsequent centrifugation is done at 2000g for 20 minutes at 4 °C within 30 minutes after collection. Following centrifugation, samples were transferred to prelabeled polypropylene vials and stored at −80 °C until biomarker quantification. Plasma concentrations of tau (Simoa Tau 2.0 Kit) and serum concentrations of NF-L (Simoa Beta Kit) were measured using digital array technology on a Simoa Single Molecule Array HD-1 Analyzer, software version 1.5. The same lot of kits was used to assay both tau and NF-L. Athletes were grouped based on their starter status, because athletes identified as starters are known to sustain a greater number of impacts. Between-group differences and time-course differences were assessed.

The scientists found that nonstarters, plasma concentrations of tau decreased over the course of the season, with lower values observed in starters; this resulted in a lower area under the curve (AUC) (starters: 416.78 ± 129.17 pg/mL/day; nonstarters: 520.84 ± 163.19 pg/mL/day). Plasma concentrations of tau could not be used to discern between starters and nonstarters. In contrast, serum concentrations of NF-L increased throughout the season as head impacts accumulated, specifically in those athletes categorized as starters. The higher serum concentrations of NF-L observed in starters resulted in a larger AUC (starters: 1,605.03 ± 655.09 pg/mL/day; nonstarters: 1,067.29 ± 272.33 pg/mL/day).

The authors concluded that the different patterns observed in serum NF-L and plasma tau concentrations provide preliminary evidence for the use of blood biomarkers to detect the neurological injury associated with repetitive subconcussive head trauma.

Jonathan M. Oliver, PhD, an Assistant Professor and the lead author of the study, said, “Given recent findings indicating a potential link between repetitive subconcussive impacts and the development of CTE, efforts to determine the effect of subconcussive impacts throughout an athlete's career may prove useful, especially if those efforts are feasible and cost effective.” The study was published on May 29, 2018, in the Journal of Neurosurgery.

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