Brain injury represents a constellation of both well- and ill-defined neurologic conditions

• Computed tomography, magnetic resonance imaging, and electroencephalography have been the diagnostic standards for brain injury
• Biologic fluid-based biomarkers have potential for aiding in diagnostics, monitoring disease, and providing therapeutic applications

Biofluid-based biomarkers for detecting brain injury in the ICU

• Biomarkers reflect the earliest changes that occur in the cells before the evidence of injury appears on images
• Proteins or protein fragments are the most common biofluid-based markers of CNS injury

Current biomarker candidates and their properties

• GFAP is an astrocyte-specific intermediate filament protein known as a marker of astrocyte activation
• UCH-L1 is a deubiquitinating enzyme highly expressed in neuronal cells and correlates with severity and outcome of injury

UCH-L1 and GFAP Assays

• UCH-L1 and GFAP assays in combination have been found to discriminate those with CT abnormalities defined clinically with mild to moderate TBI when measured within 4 hours postinjury.
• The combination of UCH-L1 and GFAP assays received US FDA clearance for testing among the mild TBI cohort.

Tau Protein

• Tau protein is an intracellular MAP with elevated levels found in CSF and serum after TBI.
• Tau protein has shown promise in predicting outcome in severe TBI, but its ability to predict outcome in mild TBI is still debated.

S100B Protein

• S100B protein is a glia-specific calcium-binding protein and is considered a prognostic biomarker of BBB permeability and CNS injury.
• Elevated S100B levels accurately reflect the presence of neuropathologic conditions, including TBI.
• Serum and urine levels of S100B after TBI have prognostic significance for survival and disability.

αII-spectrin and SBDPs