Disclosed herein are methods that aid in the determination of whether a subject has a traumatic brain injury (TBI) by detecting levels of at least one biomarker, such as ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) glial fibrillary acidic protein (GFAP), or a combination thereof, in samples taken from a subject, such as a human subject, where the subject has received a head CT scan that is negative for a TBI.