Measurement of S-100B for risk classification of victims sustaining minor head injury--first pilot study in Brazil.

BACKGROUND: Release of the neuronal protein S-100B into the circulation has been suggested as a specific indication of neuronal damage. The hypothesis that S-100B is a useful and cost-effective screening tool for the management of minor head injuries was tested.
METHODS: Fifty consecutive patients sustaining isolated minor head injury were prospectively evaluated in the emergency room of a Brazilian hospital by routine cranial computed tomography scan. Venous blood samples (processed to serum) were assayed for S-100B using a newly developed immunoassay test kit. Twenty-one normal healthy individuals served as negative controls. Data are presented as median and 25 to 75 percentiles.
RESULTS: Patients reached the emergency room an average of 45 minutes (range: 30-62 minutes) after minor head injury. Six of 50 patients (12%) showed relevant posttraumatic lesions in the initial cranial computed tomography scan and were counted as positive. The median systemic concentration of S-100B in those patients was 0.75 microg/L (range: 0.66-6.5 microg/L), which was significantly different (U-test, P < .05) from the median concentration of 0.26 microg/L (range: 0.12-0.65 microg/L), of patients without posttraumatic lesions as counted by the cranial computed tomography. A sensitivity of 100%, a specificity of 20%, a positive predictive value of 15%, and a negative predictive value of 100% was calculated for the detection of patients suffering from intracranial lesions.
CONCLUSIONS: Protein S-100B had a very high sensitivity and negative predictive value and could have an important role in ruling out the need for cranial computed tomography scan after minor head injury. This appears to be of substantial clinical relevance, particularly in countries where trauma incidence is high and medical resources are limited, such as in Brazil.