The economic impact of S-100B as a pre-head CT screening test on emergency department management of adult patients with mild traumatic brain injury.

Recent research suggests that serum S-100B may serve as a good pre-head computed tomography (CT) screening test because of its high sensitivity for abnormal head CT scans. The potential economic impact of using S-100B in the emergency department setting for management of adult patients with isolated mild traumatic brain injury (mTBI) has not been evaluated despite its clinical implementation in Europe. Using evidence from the literature, we constructed a decision tree to compare the average cost per patient of using S-100B as a pre-head CT screening test to the current practice of ordering CT scans based on patients' presenting symptoms without the aid of S-100B. When compared to scanning 45-77% of isolated mTBI patients based upon their presenting symptoms, using S-100B as a pre-head CT screen does not lower hospital costs ($281 versus $160), primarily due to its low specificity for abnormal head CT scans. Sensitivity analyses showed, however, that S-100B becomes cost-lowering when the proportion of mTBI patients being scanned exceeds 78%, or when final CT scan results require 96 min or more than the wait for blood test results. Generally speaking, if blood test results require less time than imaging, and if head CT scan rates for patients with isolated mTBI are relatively high, using S-100B will lower costs. Recommendations for using S-100B as a screening tool should account for setting-specific characteristics and their consequent economic impacts. Despite its high sensitivity and excellent negative predictive value, serum S-100B has low specificity and low positive predictive value, limiting its ability to reduce numbers of CT scans and hospital costs.