Rozga Malgorzata, Bittner Tobias, Höglund Kina, Blennow Kaj
.
Clin Chem Lab Med. 2017 Aug 28;55(10):1545-1554. doi: 10.1515/cclm-2016-1061.
A decreased level of Aβ1-42 in cerebrospinal fluid (CSF) is characteristic of Alzheimer disease and often used to support clinical diagnosis. The measured concentration of CSF Aβ1-42, however, depends strongly on several pre-analytical and analytical "confounding" factors such as sample collection, material of testing tube, CSF handling and storage procedures (e.g. transfer to new tubes after centrifugation, freeze-thaw effects). As a consequence, substantial variations in the measured levels of this biomarker are observed even for the same sample. This study investigates whether the accuracy of quantitative analysis of CSF Aβ1-42 can be improved by pre-analytical treatment of CSF with agents that could potentially reduce a freeze-thaw and adhesion-related depletion of Aβ1-42 from CSF, including modulators of Aβ aggregation and cryoprotecting or anti-adhesion agents.
The concentration of CSF Aβ1-42 was assessed with a novel Elecsys immunoassay developed for quantification of Aβ1-42 in human CSF.
Low-molecular weight Aβ oligomerization inhibitors, β-sheet breaker peptides, or the mid domain 4G8 antibody do not improve the stability of CSF Aβ1-42 during a repeated freeze-thaw treatment. Cryoprotecting agents reduce a freeze-thaw dependent loss of Aβ1-42 only when spiked to CSF to final concentration of 300 mM or higher. Adhesion of Aβ1-42 can be prevented by pre-treating CSF with Tween or by using tubes with a siliconized surface.
Between-center variability in measured level of CSF Aβ1-42 can be reduced only by standardized CSF collection into one specific tube that, without centrifugation, transfer or other types of pre-analytical processing, is directly analyzed after sample collection.
脑脊液(CSF)中Aβ1-42水平降低是阿尔茨海默病的特征,常被用于辅助临床诊断。然而,CSF中Aβ1-42的测量浓度在很大程度上取决于几个分析前和分析过程中的“混杂”因素,如样本采集、试管材质、CSF处理和储存程序(例如离心后转移至新试管、冻融效应)。因此,即使是同一样本,该生物标志物的测量水平也会有显著差异。本研究调查了使用可能减少CSF中Aβ1-42冻融和黏附相关损耗的试剂对CSF进行分析前处理,是否能够提高CSF中Aβ1-42定量分析的准确性,这些试剂包括Aβ聚集调节剂、冷冻保护剂或抗黏附剂。
采用一种新开发的用于定量检测人CSF中Aβ1-42的电化学发光免疫分析法评估CSF中Aβ1-42的浓度。
低分子量Aβ寡聚化抑制剂、β-折叠破坏肽或中结构域4G8抗体并不能改善CSF中Aβ1-42在反复冻融处理过程中的稳定性。冷冻保护剂只有在添加到CSF中使其终浓度达到300 mM或更高时,才能减少冻融依赖性的Aβ1-42损失。用吐温预处理CSF或使用表面硅化的试管可防止Aβ1-42的黏附。
只有将CSF标准化采集到一种特定的试管中,在样本采集后不经离心、转移或其他类型的分析前处理,直接进行分析,才能降低不同中心间CSF中Aβ1-42测量水平的差异。