S100b Immunoassay: An Assessment of Diagnostic Utility in Minor Head Trauma

BackgroundOver 1.4 million patients present annually to United States (US) emergency departments with minor head trauma. Many undergo unnecessary head computed tomography (HCT).ObjectivesWe sought to determine the diagnostic accuracy of S100B, a central nervous system peptide, to screen for HCT+ head injury.MethodsThis study was a prospective observational study of adults with minor head trauma. Patients presenting within 6 h 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.ResultsA 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.ConclusionThe study demonstrates that S100B may be a sensitive but non-specific marker of HCT+ injury.