Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, The Sahlgrenska Academy, University of Gothenburg, Mölndal, Sweden.
J Alzheimers Dis. 2013;33(4):1021-32. doi: 10.3233/JAD-2012-121471.
Cerebrospinal fluid (CSF) biomarkers for Alzheimer's disease (AD) are increasingly used in research centers, clinical trials, and clinical settings. However, their broad-scale use is hampered by lack of standardization across analytical platforms and by interference from binding of amyloid-β (Aβ) to matrix proteins as well as self-aggregation. Here, we report on a matrix effect-resistant method for the measurement of the AD-associated 42 amino acid species of Aβ (Aβ42), together with Aβ40 and Aβ38 in human CSF based on mass spectrometric quantification using selected reaction monitoring (SRM). Samples were prepared by solid-phase extraction and quantification was performed using stable-isotope labeled Aβ peptides as internal standards. The diagnostic performance of the method was evaluated on two independent clinical materials with research volunteers who were cognitively normal and AD patients with mild to moderate dementia. Analytical characteristics of the method include a lower limit of quantification of 62.5 pg/mL for Aβ42 and coefficients of variations below 10%. In a pilot study on AD patients and controls, we verified disease-association with decreased levels of Aβ42 similar to that obtained by ELISA and even better separation was obtained using the Aβ42/Aβ40 ratio. The developed assay is sensitive and is not influenced by matrix effects, enabling absolute quantification of Aβ42, Aβ40, and Aβ38 in CSF, while it retains the ability to distinguish AD patients from controls. We suggest this SRM-based method for Aβ peptide quantification in human CSF valuable for clinical research and trials.
脑脊液（CSF）生物标志物在阿尔茨海默病（AD）的研究中心、临床试验和临床环境中得到了越来越多的应用。然而，由于分析平台之间缺乏标准化，以及淀粉样蛋白-β（Aβ）与基质蛋白的结合以及自身聚集的干扰，其广泛应用受到了阻碍。在这里，我们报告了一种基于基质效应抵抗的方法，用于测量与 AD 相关的 42 个氨基酸的 Aβ（Aβ42），以及人类 CSF 中的 Aβ40 和 Aβ38，该方法基于使用选择反应监测（SRM）进行质谱定量。样品通过固相萃取进行制备，并使用稳定同位素标记的 Aβ 肽作为内标进行定量。该方法的诊断性能在两个具有认知正常和轻度至中度痴呆的 AD 患者的独立临床材料上进行了评估。该方法的分析特性包括 Aβ42 的定量下限为 62.5pg/mL，变异系数低于 10%。在一项针对 AD 患者和对照者的初步研究中，我们验证了与疾病相关的 Aβ42 水平降低，与 ELISA 获得的结果相似，甚至通过 Aβ42/Aβ40 比值获得了更好的分离。所开发的测定法灵敏，不受基质效应的影响，能够对 CSF 中的 Aβ42、Aβ40 和 Aβ38 进行绝对定量，同时保持区分 AD 患者和对照者的能力。我们建议将这种基于 SRM 的方法用于人类 CSF 中的 Aβ 肽定量，这对临床研究和试验很有价值。
