Stability of blood biomarkers of traumatic brain injury

Blood biomarker tests were recently approved for clinical diagnosis of traumatic brain injury (TBI), yet there are still fundamental questions that need attention. One such question is the stability of putative biomarkers in blood over the course of several days after injury if the sample is unable to be processed into serum or plasma and stored at low temperatures. Blood may not be able to be stored at ultra-low temperatures in austere combat or sports environments. In this prospective study of 20 adult patients with positive head computed tomography imaging findings, the stability of three biomarkers (glial fibrillary acidic protein [GFAP], ubiquitin C-terminal hydrolase-L1 [UCH-L1], and S100 calcium binding protein B [S100B]) in whole blood and in serum stored at 4-5°C was evaluated over the course of 72 h after blood collection. The amount of time whole blood and serum were refrigerated had no significant effect on GFAP concentration in plasma obtained from whole blood and in serum (p = 0.6256 and p = 0.3687, respectively), UCH-L1 concentration in plasma obtained from whole blood and in serum (p = 0.0611 and p = 0.5189, respectively), and S100B concentration in serum (p = 0.4663). Concentration levels of GFAP, UCH-L1, and S100B in blood collected from patients with TBI were found to be stable at 4-5°C for at least 3 days after blood draw. This study suggests that the levels of the three diagnostic markers above are still valid for diagnostic TBI tests if the sample is stored in 4-5°C refrigerated conditions.