Pre‐analytical protocol for measuring Alzheimer's disease biomarkers in fresh CSF

Introduction We aimed to establish a standardized, routine-use pre-analytical protocol for measuring Alzheimer's disease (AD) biomarkers in cerebrospinal fluid (CSF). Methods The effect of pre-analytical factors (sample collection/handling/storage/transportation) on biomarker levels was assessed using freshly collected CSF. Tube type/sterilization was assessed using previously frozen samples. A low-bind false-bottom tube (FBT, Sarstedt) was used for all experiments, except tube types/sterilization experiments. Biomarkers were measured using Elecsys CSF assays. Results Amyloid beta (Aβ)1-42 levels varied by tube type, using a low-bind FBT reduced variation. Aβ1-42 levels were higher with no mixing versus roller/inversion mixing. Aβ1-42 levels were lower with horizontal versus upright transportation; this was resolved by maximal tube filling and storage at 2°C to 8°C. Aβ1-40 levels were less strongly affected. Phospho-tau and total-tau levels were largely unaffected. Discussion We propose an easy-to-use, standardized, routine-use pre-analytical protocol, using low-bind FBTs, for measuring AD CSF biomarkers in clinical practice.