Biomarkers are important for accurate diagnosis of complex disorders such as
traumatic brain injury (TBI). For a complex and multifaceted condition such as TBI, it is likely that a single
biomarker will not reflect the full spectrum of the response of brain tissue to injury.
Ubiquitin C-terminal hydrolase L1 (UCH-L1) and
glial fibrillary acidic protein (GFAP) are among of the most widely studied
biomarkers for TBI. Because UCH-L1 and GFAP measure distinct molecular events, we hypothesized that analysis of both
biomarkers would be superior to analysis of each alone for the diagnosis and prognosis of TBI. Serum levels of UCH-L1 and GFAP were measured in a cohort of 206 patients with TBI enrolled in a multicenter observational study (Transforming Research and Clinical Knowledge in
Traumatic Brain Injury [TRACK-TBI]). Levels of the two
biomarkers were weakly correlated to each other (r=0.364). Each
biomarker in isolation had good sensitivity and sensitivity for discriminating between TBI patients and healthy controls (area under the curve [AUC] 0.87 and 0.91 for UCH-L1 and GFAP, respectively). When
biomarkers were combined, superior sensitivity and specificity for diagnosing TBI was obtained (AUC 0.94). Both
biomarkers discriminated between TBI patients with intracranial lesions on CT scan and those without such lesions, but GFAP measures were significantly more sensitive and specific (AUC 0.88 vs. 0.71 for UCH-L1). For association with outcome 3 months after injury, neither
biomarker had adequate sensitivity and specificity (AUC 0.65-0.74, for GFAP, and 0.59-0.80 for UCH-L1, depending upon Glasgow Outcome Scale Extended [GOS-E] threshold used). Our results support a role for multiple
biomarker measurements in TBI research. ( ClinicalTrials.gov Identifier NCT01565551).