Rapid elimination of protein S-100B from serum after minor head trauma.

Protein S-100B is released into the circulation after traumatic brain injury, and its serum concentration relates to measures of injury severity and outcome. These properties have led to interest in its development as a marker for clinical use, particularly in the prediction of adverse outcome for those with apparently trivial injuries. Before it can be used in populations of patients with head injuries, however, more needs to be understood about its release and elimination. This study was designed to estimate the elimination half-life of S-100B from the circulation after minor head trauma. We studied 14 patients with minor head injuries and measured serum S-100B serially after initial assessment in the Emergency Department of an inner city teaching hospital. We used curve-fit analysis to estimate the elimination constant that best fitted our data, and from this estimated the elimination half-life of protein S-100B. We estimated the mean half-life in this setting to be 97 min (95% confidence interval [CI] of 75-136 min). S-100B is cleared rapidly, relative to the time elapsed between injury and initial assessment in the Emergency Department. Variation in the time elapsed between injury and sampling is likely to influence the accuracy of head injury outcome prediction based on S-100B concentrations in serum, and should be considered when designing future studies.