Table 1.

Inclusion and exclusion criteria

Inclusion Criteria for suspected TBI cases

• Adults between the ages of 18 and 90

• Blunt traumatic head injury presenting to the ED within 24 hours of injury

• Meet the ACEP criteria* for receiving a head CT scan in the setting of suspected TBI, namely:

○ Loss of consciousness (LOC) or post-traumatic amnesia (PTA) and one or more of the following: focal neurologic deficit, headache, vomiting, age >60 years, drug or alcohol intoxication, deficits in short-term memory, physical evidence of trauma above the clavicle, posttraumatic seizure, Glasgow Coma Score (GCS) <15, or coagulopathy

○ No LOC or PTA, but one of the following: focal neurologic deficit, severe headache, vomiting, age >65 years, physical signs of a basilar skull fracture, GCS < 15, coagulopathy, dangerous mechanism of injury (ejection from a motor vehicle, a pedestrian struck, or a fall from a height >3 feet or 5 stairs)

• Receive a routine head CT scan in the ED

Exclusion Criteria for suspected TBI cases

• Initial blood sample not obtained within 24 hours of injury

• Received blood transfusion before initial blood draw

• Head injury is seizure-induced

• Exclusion criteria common to all groups (see below)

Inclusion Criteria for traumatic injury without evidence of head trauma

• Adults between the ages of 18 and 90

• Traumatic injury including fracture, sprain, ligamentous injury, laceration

• No direct injury to head or significant accelerating/decelerating forces associated with injury mechanism

Exclusion Criteria for traumatic injury without evidence of head trauma

• Unable to recall whether head was injured

• Altered mental status or unreliable historian

• Initial blood sample not obtained within 24 hours of injury

• Received blood transfusion before initial blood draw

• Traumatic injury is seizure-induced

• Past medical history of stroke with neurological deficits, demyelinating disease, neurodegenerative disease

• Exclusion criteria common to all groups (see below)

Inclusion Criteria for healthy persons

• Adults between the ages of 18 and 90

Exclusion Criteria for healthy persons

• Any active illness

• Recent blood transfusion

• Past medical history of stroke with neurological deficits, demyelinating disease, neurodegenerative disease, or renal failure

• Blood pressure currently over 140/80

• Recreational drug use within last 2 weeks (alcohol acceptable as long as not clinically intoxicated)

• Exclusion criteria common to all groups (see below)

Exclusion Criteria common to all groups

• Cannot communicate in English

• No working telephone number

• Currently pregnant

• Past medical history of intracranial surgery, intracranial hemorrhage (traumatic or non-traumatic), brain tumor, dementia (mild and moderate dementia allowed in TBI group)

ACEP Criteria = American College of Emergency Physicians criteria for a head CT in the setting of suspected TBI [13].