Impact of CSF storage volume on the analysis of Alzheimer's disease biomarkers on an automated platform

Abstract Objectives To assess the potential influence of the ratio between the storage tube surface area and the volume of cerebrospinal fluid (CSF) (surface/volume) on the quantifications of four Alzheimer's disease (AD) biomarkers on the Lumipulse G600II automated platform. Methods CSF samples of 10 consecutive patients were stored in 2 ml polypropylene tubes containing four different CSF volumes: 1.5 ml, 1 ml, 0.5 ml and 0.25 ml. Concentration of CSF Aβ1-42, Aβ1–40, t-Tau and p-Tau were measured in all aliquots using the LUMIPULSE G600II automated platform from Fujirebio. Results Levels of CSF Aβ1-42 and Aβ1-40 were lower in samples stored with lower volumes (higher surface/volume ratios). This decrease was partly compensated by using the ratio Aβ1-42/Aβ1-40. Quantification of t-Tau and p-Tau were not influenced by this pre-analytical condition. Conclusion The surface/volume ratio can potentially influence the results of amyloid AD biomarkers. It appears essential to take into account the surface/volume ratio of the storage tubes when quantifying CSF biomarkers in clinical routine.