Influence of Simulated Pre-Hospital Transport, Time to Analysis, and Storage Temperature on S100 Calcium-Binding Protein B Values

According to in-hospital guidelines, the biomarker, S100 calcium-binding protein B (S100B), is used to rule out intracranial lesions in mild-moderate traumatic brain injury (TBI). It is currently investigated whether S100B is applicable in a pre-hospital setting. The aim was to compare S100B values and hemolysis index in blood samples drawn and stored under simulated pre-hospital conditions to standardized blood samples. Thirty patients undergoing craniotomy at Department of Neurosurgery, Aarhus University Hospital (Aarhus, Denmark) each had six blood samples drawn. Two samples, drawn in in-hospital standardized Beckton Dickinson tubes and pre-hospital Monovette tubes, respectively, were stored as references at 21°C for 30 min. Two samples were stored at 15°C and 29°C, respectively, one sample was stored at prolonged time (60 min), and one sample was transported for 30 min before centrifugation. S100B values were compared by equivalence test with a pre-defined equivalence margin of ±8.5%. There was no clinically relevant difference between samples stored in different tubes, at various temperatures, or time to analysis compared to reference samples. Transported samples had an 11.5% (90% confidence interval [CI], 6.55; 16.61) higher median S100B value and a 430% (95% CI, 279.6; 661.4) higher median hemolysis index compared to reference samples. Three of 30 (10%) patients had an S100B value above guideline cutoff in the transported sample, which was not found in reference samples (false positive). There were no false negatives. In conclusion, S100B values were not influenced by different tubes, temperatures, and time to analysis. Transported samples had higher median S100B values and hemolysis, icterus, and lipemia index compared to reference samples.