Protein S-100b as a screening tool for the need of head CT scan after minor head trauma

Introduction

Systematic use of head CT scan after minor head trauma may lead to a high incidence of negative examinations and high costs. On the other hand, undetected intracranial lesions may be life threatening. Neuronal protein S-100b into the circulation has been suggested as a specific indication of neuronal damage. We tested the hypothesis that protein S-100b is a useful and cost-effective screening tool for the management of minor head traumas.

Methods

Fifty consecutive patients sustaining isolated minor head trauma were prospectively evaluated in the emergency room by routine head CT scan and blood sampling for protein S-100b measurement, using an immunoluminescence test kit. Seventeen normal healthy individuals served as negative controls. Data are presented as the median and 25th–75th percentiles.

Results

Patients reached the emergency room 45 min (30–62 min) after minor head trauma. Six patients had relevant post-traumatic lesions at the initial head CT (12%) and were thereby counted as positive (CT+). The median systemic concentration of S-100b in those patients was 0.75 μg/l (0.61–6.5 μg/l), which was significantly different (U-test, P = 0.011) from the median concentration, 0.26 μg/l (0.12–0.65 μg/l), of those without post-traumatic lesions in the initial head CT scan (CT-). A sensitivity of 100%, a specificity of 20%, a positive predictive value of 15% and a negative predictive value of 100% were detected.

Conclusions

Protein S-100b has a very high sensitivity and negative predictive value, and could have an important role in ruling out the need for CT scan after minor head trauma. This may be of clinical relevance, particularly in countries in which trauma is epidemic and medical resources are limited, such as in Brazil.