A Study to Develop a Blood-based Test for Aiding the Diagnosis/Prognosis of Traumatic Brain Injury in Adults and for Monitoring the Development of Secondary Events in Patients Diagnosed With Traumatic Brain Injury

Inclusion Criteria: * Presenting to the Emergency Department with a biomechanically plausible mechanism of non-penetrating traumatic brain injury (TBI; direct impact: blow to the head, head against object, object against head; acceleration/deceleration) * Acute brain CT completed for standard of care Further Inclusion Criteria (specific for CLIN12.2): * Admitted to the hospital with radiographic evidence of acute TBI * Admitted to the intensive care unit at risk for decline related to TBI Exclusion Criteria: * Prior neurosurgical intervention within the last 6 months * Major debilitating neurological disease (such as, but not limited to: stroke, CVA, mild cognitive impairment, Alzheimer's disease, Amyotrophic lateral sclerosis, Parkinson's disease, Huntington's disease, Frontotemporal dementia, tumor, epilepsy, unmanaged seizure disorder), impairing baseline awareness, cognition, or validity of outcomes assessments * Major debilitating baseline mental health disorders (such as but not limited to schizophrenia or bipolar disorder) that would interfere with follow-up and the validity of outcome assessments * Significant pre-existing conditions that would interfere with follow-up and outcome assessment (such as, but not limited to: chronic kidney disease, chronic cardiovascular comorbidities, alcohol or substance use disorder) * History of melanoma * Primary diagnosis of ischemic or hemorrhagic stroke * Any spinal Cord Injury (American Spinal Injury Association \[ASIA\] score of A-D) * Received chemotherapy or radiation currently or within the last year * Patients on psychiatric hold (e.g., 5150, 5250) * Current incarceration or in custody * Known inability to undergo an MRI * Currently receiving any interventional treatments as a part of an investigational study/trial (drug, device, behavioral, treatment) at the time of enrollment and/or during the course of this study * Low likelihood of follow-up (e.g. participant or family indicating low interest, residence in another state or country, homelessness or lack of reliable contacts) * Any condition that, in the opinion of the investigator, could interfere in the proper execution of the study procedures and/or in their future permanence in the study