Influence of delayed CSF storage on concentrations of phospho-tau protein (181), total tau protein and beta-amyloid (1–42)

Abstract

It is generally accepted that cerebrospinal fluid (CSF) biomarkers such as tau protein, phosphorylated tau protein (threonine 181) and beta-amyloid (1–42) can facilitate early and differential diagnosis of Alzheimer's disease (AD). Since the respective concentrations can only be measured in a number of specialized centers, time to CSF specimen work-up has been considered as crucial for the stability of the respective biomarkers. When shipping of CSF samples is needed for biomarker measurement and immediate freezing of samples is not available, an overnight delay of up to 24 h frequently occurs. Therefore, we investigated the potential impact of a 24 h delayed freezing on CSF biomarker concentrations and compared it to 2 h storage (room temperature, 20 °C) and an immediate freezing. First, storage at room temperature for 2 h had only marginal, non-significant effects on the concentrations of CSF total tau protein and phospho-tau protein (181) compared to immediate freezing. Second, storage at room temperature for 24 h did not significantly affect total tau protein or phospho-tau protein but beta-amyloid (1–42) concentrations which increased significantly compared to the samples frozen immediately. These results indicate that CSF samples for the evaluation of total tau and phospho-tau protein may be kept at room temperature for up to 24 h whereas CSF samples for beta-amyloid (1–42) need to be frozen immediately.