Ashton, Nicholas J.Suárez-Calvet, MarcKarikari, Thomas K.Lantero Rodriguez, JuanSnellman, AnniinaSauer, MathiasSimrén, JoelMinguillón, CarolinaFauria, KarineBlennow, KajZetterberg, Henrik2021-12-202021-12-202021Ashton NJ, Suárez-Calvet M, Karikari TK, Lantero-Rodriguez J, Snellman A, Sauer M, Simrén J, Minguillon C, Fauria K, Blennow K, Zetterberg H. Effects of pre-analytical procedures on blood biomarkers for Alzheimer's pathophysiology, glial activation, and neurodegeneration. Alzheimers Dement (Amst). 2021;13(1):e12168. DOI: 10.1002/dad2.121682352-8729http://hdl.handle.net/10230/49254Introduction: 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 < .0001), and minor decreases in EDTA Aβ40 and EDTA p-tau181 were found after freeze-thaw cycle 4 (P < .05). Discussion: The same tube type should be used in research studies on blood biomarkers. Individual concentration cut-offs are needed for each tube type in all tested biomarkers despite being highly correlated. Serum should be avoided for Aβ42, Aβ40, and t-tau. Freeze-thaw cycles > 3 should be avoided for p-tau181.application/pdfeng© 2021 The Authors. Alzheimer's & Dementia: Diagnosis, Assessment & Disease Monitoring published by Wiley Periodicals, LLC on behalf of Alzheimer's Association. This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.info:eu-repo/semantics/articlehttp://dx.doi.org/10.1002/dad2.12168Amyloid betaBiomarkersBloodCitrateEthylenediaminetetraacetic acidGlial fibrillary acidic proteinLithium heparinNeurofilament lightPhosphorylated tauPre‐analyticsSeruminfo:eu-repo/semantics/openAccess