Diagnostic performance of biomarker S100B and guideline adherence in routine care of mild head trauma

BACKGROUND: The Scandinavian Neurotrauma Committee (SNC) has recommended the use of serum S100B as a biomarker for mild low-risk Traumatic brain injuries (TBI). This study aimed to assess the adherence to the SNC guidelines in clinical practice and the diagnostic performance of S100B in patients with TBI. The aims of this study were to examine adherence to the SNC guideline and the diagnostic accuracy of serum protein S100B. METHODS: Data of consecutive patients of 18 years and above who presented to the emergency department (ED) at Helsingborg Hospital with isolated head injuries, were retrieved from hospital records. Patients with multitrauma, follow-up visits, and visits managed by a nurse without physician involvement were excluded. RESULTS: A total of 1671 patients were included of which 93 (5.6%) had intracranial hemorrhage. CT scans were performed in 62% of patients. S100B was measured in 26% of patients and 30% of all measurements targeted the low-risk mild head injuries indicated by the guideline. S100B's recommended cut-off value (≥ 0.10 µg/L) had a 100% sensitivity, 47% specificity, 10.1% positive predictive value, and 100% negative predictive value—if applied to the target SNC category (SNC 4). If applied to all patients tested, the sensitivity was 93% for traumatic intracranial hemorrhage (TICH). Current ED practices were adherent to the SNC guideline in 55% of patients. Non-adherent practices occurred in 64% of patients with low-risk mild head injuries (SNC4) including overtesting or undertesting of S100B and CT scans. CONCLUSION: Adherence to guidelines was low and associated with a higher admission rate than non-adherence practice but no significant increase in missed TICH or death associated with non-adherence to guideline was found. In routine care, we found that the sensitivity and NPV of serum protein S100B was excellent and safely ruled out TICH when measured in the patient category recommended by the guideline. However, measuring serum protein S100B in patients not recommended by the guideline rendered unacceptably low sensitivity with possible missed TICHs as a consequence. To further delineate the magnitude and impact of non-adherence, more studies are needed.