Negative predictive value of S100B in all types of traumatic brain injury in different aging groups

Traumatic brain injury (TBI) represents a major contributor to global morbidity and mortality, and the optimization of diagnostic approaches continues to be a matter of considerable scientific debate. The S100 calcium-binding protein B (S100B) value is characterized by a high diagnostic negative predictive value (NPV) and is obtained without exporure to radiation. The aim of the study was to investigate the NPV of the S100B level in the patient cohort aged 75 and older with TBI and compare the results with a cohort of individuals below 75. The hypothesis was, that the S100B value would have a sufficiently high NPV in both patient groups, thereby serving as a diagnostic marker, but with a higher NPV in the below 75 age group. A retrospective study was conducted on 815 TBI patients from a Level I trauma center from April 2016 to May 2024. Both, S100B levels and CT scans were obtained within 30 min to 6 h post-trauma. Patients were divided into two groups: below 75 years and 75 years and older. S100B levels ≥ 0.105 µ/L were considered positive.NPV and sensitivity were calculated for both groups. Among the 815 patients, 76 had normal S100B and CT results, 13 had abnormal CT but normal S100B, 65 had elevated S100B and abnormal CT, and 661 had elevated S100B with normal CT. The overall NPV was 85.4% (95% CI 0.753, 0.909; p < 0.01), with a sensitivity of 83.3% (95% CI 0.776, 0.919; p < 0.01). In the under-75 group (574 patients), the NPV was 86.8% (95% CI 0.816, 1; p < 0.01), and sensitivity was 76.2% (95% CI 0.5, 1; p < 0.01). In the over-75 group (241 patients), the NPV was 77% (95% CI 0.622, 0.878; p < 0.01), with sensitivity of 91.7% (95% CI 0.786, 0.938; p < 0.01). The intervention rate was 0.3% in the under-75 group and 1.6% in the over-75 group. We found a clear and significant correlation between a negative S100B level and normal CT scan. We believe that the determination of S100B levels significantly reduces the radiation exposure for TBI patients, especially in younger patients. However, its reliability varies by age, warranting further investigation in diverse populations and TBI severities.