Importance of cerebrospinal fluid storage conditions for the Alzheimer's disease diagnostics on an automated platform.

Abstract

Alzheimer's disease (AD) is considered the most common cause of dementia in older people. Cerebrospinal fluid (CSF) Aβ1-42, Aβ1-40, total Tau (t-Tau), and phospho Tau (p-Tau) are important biomarkers for the diagnosis, however, they are highly dependent on the pre-analytical conditions. Our aim was to investigate the potential influence of different storage conditions on the simultaneous quantification of these biomarkers in a fully-automated platform to accommodate easier pre-analytical conditions for laboratories. CSF samples were obtained from 11 consecutive patients. Aβ1-42, Aβ1-40, p-Tau, and t-Tau were quantified using the LUMIPULSE G600II automated platform. Temperature and storage days significantly influenced Aβ1-42 and Aβ1-40 with concentrations decreasing with days spent at 4°C. The use of the Aβ1-42/Aβ1-40 ratio could partly compensate it. P-Tau and t-Tau were not affected by any of the tested storage conditions. For conditions involving storage at 4°C, a correction factor of 1.081 can be applied. Diagnostic agreement was almost perfect in all conditions. Cutoffs calculated in samples stored at-80°C can be safely used in samples stored at-20°C for 15-16days or up to two days at RT and subsequent freezing at-80°C. For samples stored at 4°C, cutoffs would require applying a correction factor, allowing to work with the certainty of reaching the same clinical diagnosis.