S100b immunoassay: an assessment of diagnostic utility in minor head trauma.

Background: Over 1.4 million patients present annually to United States (US) emergency departments with minor head trauma. Many undergo unnecessary head computed tomography (HCT).

Objectives: We sought to determine the diagnostic accuracy of S100B, a central nervous system peptide, to screen for HCT+ head injury.

Methods: This study was a prospective observational study of adults with minor head trauma. Patients presenting within 6h of injury and undergoing HCT for evaluation were eligible. All HCTs were blindly reviewed for presence of a priori defined intracranial injury (HCT+). Quantitative S100B levels were determined by enzyme-linked immunosorbent assay.

Results: A total of 346 patients were enrolled over 12 months, mean age 48 years (± 23 years), 62% male. Twenty-two (6.4%) were HCT+. Vomiting, headache, anterograde amnesia, Glasgow Coma Scale score<15, nausea, and loss of consciousness were associated with HCT+ results. Median S100B levels were significantly elevated in HCT+ (115 ng/dL) vs. HCT- (56.0 ng/dL) patients (p=0.032). Receiver operator characteristic analysis demonstrated an area under the curve of 0.643. Sensitivity and specificity were 86% (95% confidence interval [CI] 67-96) and 37% (95% CI 29-45%) at 42 ng/dL, 91% (95% CI 72-98%) and 24% (95% CI 17-31%) at 32 ng/dL, and 96% (95% CI 78-100%) and 13% (95% CI 9-20%) at 24 ng/dL, respectively.

Conclusion: The study demonstrates that S100B may be a sensitive but non-specific marker of HCT+ injury.