Figure 1. Flowchart of study participants.

Flowchart shows study participants in the 2 study cohorts. The first cohort included 45 professional ice hockey players with acute concussion sampled at 6 days after a sports-related concussion, 31 professional hockey players with postconcussion symptoms (PCS) due to repetitive concussions, 28 ice hockey players who underwent blood sampling at preseason, and 14 healthy controls. The players with persistent PCS due to repetitive concussions and healthy controls also underwent paired CSF and serum assessment. The second cohort includes 162 clinic-based patients with subacute and chronic traumatic brain injury (TBI) and 68 healthy controls after the exclusion 17 participants due to screen failure. Of 162, 102 underwent repeated blood, imaging, and functional assessments up to 5 years.