The clinical value of serum S-100 protein measurements in minor head injury: a Scandinavian multicentre study

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Abstract
Purpose: This study of patients with minor head injury was designed to investigate the relation of S-100 protein measurements to computed tomograpy (CT) findings and patients outcomes. Increased serum levels of this protein were hypothetized to predict intracranial pathology and increased frequency of post-concussion symptoms. Methods: One hundred and eighty-two patients were studied with Glasgow Coma Scale scores of 13-15. The study recruited patients from three Scandinavian neurotrauma centres. Serum levels of S-100 protein were measured at admittance and CT scans of the brain were obtained within 24 hours postinjury in all patients. Outcome was evaluated with the Rivermead Postconcussion Symptoms Questionnaire (RPQ) 3 months after the injury. Results: Increased serum level of S-100 protein was detected in 69 (38%) patients, and CT scan demonstrated intracranial pathology in 10 (5%) (brain contusion in seven, epidural haematoma in two, traumatic subarachnoid haemorrhage in one). The proportion of patients with detectable serum level was significantly (p < 0.01) higher among those with intracranial pathology (90%) compared to those without (35%). The negative predictive value of an undetectable S-100 level was 0.99. Sixty-two per cent reported one or more post-concussion symptoms at follow-up. A trend was observed towards an increased frequency of post-concussion symptoms among patients with detectable serum levels. Conclusions: Undetectable serum level of S-100 protein predicts normal intracranial findings on CT scan. Determination of S-100 protein in serum may be used to select patients for CT scanning. Increased S-100 serum levels may be more related to post-concussion symptoms caused by mild traumatic brain injury than to symptoms of psychological origin.