GFAP and S100B in the acute phase of mild traumatic brain injury.

OBJECTIVE: The biomarkers glial fibrillary acid protein (GFAP) and S100B are increasingly used as prognostic tools in severe traumatic brain injury (TBI). Data for mild TBI are scarce. This study aims to analyze the predictive value of GFAP and S100B for outcome in mild TBI and the relation with imaging.

METHODS: In 94 patients biomarkers were determined directly after admission. Collected data included injury severity, patient characteristics, admission CT, and MRI 3 months postinjury. Six months postinjury outcome was determined with Glasgow Outcome Scale Extended (GOSE) and return to work (RTW).

RESULTS: Mean GFAP was 0.25 μg/L (SD 1.08) and S100B 0.54 μg/L (SD 1.18). In 63% GFAP was not discernible. GFAP was increased in patients with an abnormal CT (1.20 μg/L, SD 2.65) compared to normal CT (0.05 μg/L, SD 0.17, p < 0.05). Also in patients with axonal injury on MRI GFAP was higher (0.65 μg/L, SD 0.91 vs 0.07 μg/L, SD 0.2, p < 0.05). GFAP was increased in patients with incomplete RTW compared to complete RTW (0.69 μg/L, SD 2.11 vs 0.12 μg/L, SD 0.38, p < 0.05). S100B was not related to outcome or imaging studies. In multivariate analysis GFAP was not predictive for outcome determined by GOSE and RTW.

CONCLUSIONS: A relation between GFAP with imaging studies and outcome (determined by RTW) was found in contrast to S100B. As the positive predictive value of GFAP is limited in this category of TBI patients, this biomarker is not suitable for prediction of individual patient outcome.