Department of Psychiatry and Psychotherapy, Universitätsklinikum Erlangen and Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany.
J Alzheimers Dis. 2011;25(4):739-45. doi: 10.3233/JAD-2011-110212.
Preanalytical sample handling and storage procedures play an extremely important role in reliably measuring neurochemical dementia diagnostics (NDD) biomarkers: Aβ(1-40), Aβ(1-42), Tau, and pTau181. To test different handling and storage conditions, the following protocols were applied: (a) storage at room temperature for one week, (b) deep-freezing and thawing up to three cycles, (c) deep-freezing, thawing and keeping under +4°C for two days before the analysis, and (d) long-term stability of a deeply frozen sample. Between the first and the seventh day of the storage at room temperature, the percentage of the concentrations (compared to the starting concentrations) fluctuated: 104.3-105.3, 97.6-93.2, 100.6-96.8, and 97.9-90.2 for Aβ(1-40), Aβ(1-42), Tau, and pTau181, respectively. Re-freezing cycles resulted in the percentage fluctuations of the concentrations: 101.1-105.5, 95.4-99.7, 98.3-100.0, and 100.5-101.4 for Aβ(1-40), Aβ(1-42), Tau, and pTau181, respectively. Keeping previously frozen/thawed samples under +4°C for two days resulted in the percentage differences of the concentrations: +15.9, +2.2, -1.1, and -0.1 for Aβ(1-40), Aβ(1-42), Tau, and pTau181, respectively. During long-term stability, the coefficients of linear correlation (R(2)) were: Aβ(1-40), 0.007; Aβ(1-42), 0.02; Tau, 0.011; and pTau181, 0.02, and the corresponding inter-assay coefficients of variation: 13.9%, 13.9%, 11.0%, and 10.7% for Aβ(1-40), Aβ(1-42), Tau, and pTau181, respectively. We conclude that the NDD biomarkers are relatively stable when the cerebrospinal fluid sample is kept at room temperature for about four days; one or two thawing/refreezing cycles do not profoundly affect the biomarkers concentrations, however three cycles result in increased unsystematic variation. The four biomarkers seem to be stable in a sample stored deeply frozen for more than two years.
在可靠地测量神经化学痴呆诊断（NDD）生物标志物：Aβ（1-40）、Aβ（1-42）、Tau 和 pTau181 方面，预分析样本处理和储存程序起着极其重要的作用。为了测试不同的处理和储存条件，采用了以下方案：（a）在室温下储存一周，（b）深冻和解冻多达三个循环，（c）深冻、解冻并在分析前保持在+4°C 下两天，以及（d）深冻样本的长期稳定性。在室温下储存的第一天到第七天之间，浓度的百分比波动如下：Aβ（1-40）为 104.3-105.3%、Aβ（1-42）为 97.6-93.2%、Tau 为 100.6-96.8% 和 pTau181 为 97.9-90.2%。再冷冻循环导致浓度百分比波动：Aβ（1-40）为 101.1-105.5%、Aβ（1-42）为 95.4-99.7%、Tau 为 98.3-100.0% 和 pTau181 为 100.5-101.4%。将先前冷冻/解冻的样品保持在+4°C 下两天会导致浓度的百分比差异：Aβ（1-40）为+15.9%、Aβ（1-42）为+2.2%、Tau 为-1.1% 和 pTau181 为-0.1%。在长期稳定性期间，线性相关系数（R（2））为：Aβ（1-40）为 0.007；Aβ（1-42）为 0.02；Tau 为 0.011；pTau181 为 0.02，相应的批内变异系数为：Aβ（1-40）为 13.9%、Aβ（1-42）为 13.9%、Tau 为 11.0% 和 pTau181 为 10.7%。我们得出结论，当脑脊液样本在室温下保存约四天时，NDD 生物标志物相对稳定；一个或两个解冻/再冷冻循环不会深刻影响生物标志物浓度，但三个循环会导致非系统性变化增加。这四种生物标志物在深冻储存超过两年的样本中似乎稳定。
