Serum Biomarkers for Brain Death Diagnosis

Introduction to S100B

• S100B is an astrocyte-specific CNS protein that is released following neuronal injury and crosses the disrupted blood-brain barrier into peripheral circulation, with a short half-life of approximately 97 minutes, making timing of measurement crucial 1, 2, 3, 4, 5, 6

Limitations of S100B Measurement

• S100B measurements are highly sensitive to hemolysis, which can produce false-positive results, and standards for S100B measurement vary between centers, making comparison of absolute values difficult 8
• Extracerebral sources, such as adipocytes, chondrocytes, skin, and cartilage, can lead to false elevations in patients with significant extracranial injuries 6, 7

Alternative Biomarkers

• An elevated CSF/serum albumin ratio indicates blood-brain barrier disruption and is the standard biomarker for BBB integrity, with a ratio >20 strongly indicating BBB disruption 4, 5, 9
• NSE levels in CSF are proportional to TBI severity and associated with increased mortality in moderate or severe TBI, but should not be used alone to predict neurological outcomes due to high false-positive rates 8