Diagnostic value of Elecsys S100 as a marker of acute brain injury in the emergency department.

The aim of this study was to evaluate the screening and diagnostic validity of the initial serum S100 levels by Elecsys S100 immunoassay in an emergency department. We measured serum S100 in 101 acute brain injury (ABI) patients, in 40 healthy subjects, and in 41 chronic brain injury (CBI) patients (the control group). The ABI patients were divided in several groups according to the Glasgow Coma Scale (GCS), injury type and findings of brain imaging. Of the 101 patients, the 66 cranial computed tomography (CCT) or brain magnetic resonance imaging (MRI)-positive patients showed higher S100 levels than did the 35 CCT/MRI-negative patients (P=0.028). At a cutoff of 0.105 microg/L, the sensitivity was 84.8% and the specificity 74.3% for all of the ABI patients, and the sensitivity was increased to 96.9% for the traumatic ABI patients for detecting image-positive ABI. There was no significant difference of S100 levels among the groups on the CCT or MRI pathological findings (P=0.478). In conclusion, serum S100 levels can be used in the emergency department as an additional screening tool to identify CCT- or MRI-positive ABI.