Urinary S100B concentrations are increased after brain injury in children: A preliminary study*

OBJECTIVE: S100B is a renally excreted protein concentrated in glial cells of the nervous system. Increases in serum S100B concentrations reflect brain injury. However, increases in serum are rapid and transient and therefore may be of limited use in certain patients. Urinary S100B concentrations may be able to provide information about brain injury in this subgroup of patients. DESIGN: Prospective, descriptive study. SETTING: Level I trauma center. PATIENTS: Fifteen children with acute traumatic or hypoxemic brain injury (subjects) and 14 healthy controls. INTERVENTIONS: Urine and serum samples were collected from subjects and controls. Serial samples were collected in brain injury subjects up to every 12 hrs for 3 days. S100B concentrations were measured by enzyme-linked immunosorbent assay (Nanogen, San Diego CA). Outcome was assessed by Glasgow Outcome Scale score. MEASUREMENTS AND MAIN RESULTS: Urinary S100B concentrations were detectable in 80% of subjects with increased serum S100B concentrations and 0% of controls. Peak urinary S100B concentrations occurred significantly later than peak serum S100B concentrations: 55.3 (29.8) (mean [sd]) vs. 14.6 (11.8) hrs after injury (p = .002). All subjects with an undetectable urinary S100B had a good outcome vs. only 20% of subjects with a detectable urinary S100B. Subjects with increased serum S100B were more likely to have a poor outcome than those with normal S100B (p = .01). CONCLUSIONS: Increases in urinary S100B are found in the majority of children with acute brain injury and an increased serum S100B. Urinary S100B concentrations peak later than serum concentrations, suggesting that measurement of urinary S100B may be helpful in subjects in whom early serum S100B is unavailable. Urinary and/or serum S100B concentrations may be useful to assist in the prediction of outcome after pediatric brain injury.