Effects of pre‐analytical procedures on blood biomarkers for Alzheimer's pathophysiology, glial activation, and neurodegeneration

Abstract Introduction We tested how tube types (ethylenediaminetetraacetic acid [EDTA], serum, lithium heparin [LiHep], and citrate) and freeze–thaw cycles affect levels of blood biomarkers for Alzheimer's disease (AD) pathophysiology, glial activation, and neuronal injury. Methods Amyloid beta (Aβ)42, Aβ40, phosphorylated tau181 (p‐tau181), glial fibrillary acidic protein, total tau (t‐tau), neurofilament light, and phosphorylated neurofilament heavy protein were measured using single molecule arrays. Results LiHep demonstrated the highest mean value for all biomarkers. Tube types were highly correlated for most biomarkers (r > 0.95) but gave significantly different absolute concentrations. Weaker correlations between tube types were found for Aβ42/40 (r = 0.63–0.86) and serum t‐tau (r = 0.46–0.64). Freeze–thaw cycles highly influenced levels of serum Aβ and t‐tau (P 3 should be avoided for p‐tau181.