Is there a clinical benefit of S100B for the management of mild traumatic brain injury?

Objective: Mild traumatic brain injuries (mTBIs) account for approximately 90% of traumatic brain injuries and are a common cause for hospitalization. Cranial CT (CCT) is the preferred diagnostic tool, but 85%-99% of mTBI patients show no visible lesions on CCT, making its use controversial due to radiation risks and costs. To identify mTBI patients requiring CCT, serum S100B concentrations have been integrated in international guidelines. However, its short half-life and low specificity to detect intracranial hemorrhages (IHs) in mTBI are frequently discussed limitations. The aim of this study was to determine the clinical benefit of S100B in reducing unnecessary CCT studies at a high-volume trauma center.

Methods: The authors retrospectively analyzed the data of mTBI patients who were admitted to an urban level I trauma center between January 2017 and December 2022. They included all adult mTBI patients who underwent S100B measurement and had a subsequent CCT study. Patients who underwent immediate CCT on admission per the Canadian CT Head Rule or in the case of antithrombotic therapy were excluded.

Results: A total of 391 patients with a mean age of 46 years were included. IH was detected in 23 mTBI patients (5.9%), with 2 patients (0.51%) requiring neurosurgical intervention. The mean S100B level was 0.21 μg/L (range 0.03-2.27 μg/L), with a cutoff at 0.105 μg/L. Patients with positive CCT findings had a mean S100B level of 0.31 μg/L, compared with 0.21 μg/L for negative CCT cases (p = 0.011). IHs occurred in 6.1% of patients with elevated S100B levels and in 4.2% of patients with normal S100B values. The specificity of S100B for positive CCT findings was 12.5%, with a positive predictive value of 6.1% and a negative predictive value of 95.8%. False-positive results led to 57 unnecessary CCT studies annually.

Conclusions: This study emphasizes the need for careful consideration when integrating S100B into mTBI management protocols for patients with a low risk for IHs. The low specificity in a younger population suggests that the risks of radiation from unnecessary CCT studies may outweigh the benefits. Although international guidelines were followed, integrating S100B into the mTBI protocol did not reduce CCT use as expected. In the absence of ongoing or new onset of neurological symptoms, elevated S100B values should not trigger CCT studies in a low-risk mTBI population.