According to the Centers for Disease Control and Prevention, approximately 200,000 hospitalizations occurred in 2020 related to Traumatic Brain Injury (TBI), which does not include many TBIs treated only in emergency departments, urgent care, primary care, or that are not evaluated by a clinician. Head CT is a critical component of care for severe TBI, however in mild TBI there is practice variation with a wider risk to benefit estimation for obtaining head CT imaging. Potential disadvantages of head CT include longer Emergency Department (ED) length of stay (LOS), higher costs, and diagnostic radiation exposure. The i-STAT TBI test is a panel of in vitro diagnostic immunoassays for the quantitative measurements of glial fibrillary acidic protein (GFAP) and ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) in whole blood and a semi-quantitative interpretation of test results derived from these measurements, using the i-STAT Alinity instrument. This biomarker test is cleared for use in adults with mild TBI (Glasgow Coma Scale 13-15) within 24 hours of injury, to aid in determining the need for head CT imaging. Currently, CT head imaging for adults with suspected mild TBI is obtained based on clinicians' usual practice patterns and beliefs about patient expectations. Prior research has demonstrated the blood TBI test may reduce unnecessary CT scans by up to 40%, however the impact on head CT ordering has not yet been studied prospectively. It is important to understand the extent to which a negative TBI biomarker result empowers a clinician to cancel a previously ordered head CT. Given that adult patients with mild TBI often present to EDs, which have access to CT scanners, this is a key setting to assess real-world impact of the i-STAT TBI test on CT head utilization.