Department of Neuroscience, University of Minnesota, Minneapolis, MN, USA.
Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis, MN, USA.
J Alzheimers Dis. 2023;95(2):735-748. doi: 10.3233/JAD-230384.
Sample collection and preanalytical protocols may significantly impact the results of large-scale epidemiological studies incorporating blood-based biomarkers of neuropathology.
To evaluate the stability and assay variability of several blood-based biomarkers of neuropathology for common preanalytical conditions.
We collected serum and plasma samples from 41 participants and evaluated the effect of processing delay of up to 72 h when stored at 4∘C, three freeze-thaw cycles, and a combination of 48-h processing delay when stored at 4∘C and three freeze-thaw cycles on biomarker stability. Using the Simoa assay (Quanterix Inc.), we measured amyloid-β 40 (Aβ40), amyloid-β 42 (Aβ42), neurofilament light (NfL), glial fibrillary acidic protein (GFAP), and phosphorylated tau 181 (p-tau-181).
We found that Aβ40 and Aβ42 levels significantly decreased after a 24-h processing delay in both plasma and serum samples, and a single freeze-thaw cycle (p < 0.0001). Nevertheless, serum Aβ42/40 ratio remained stable with a processing delay up to 48 h while plasma Aβ42/40 ratio showed only small but significant increase with a delay up to 72 h. Both plasma and serum GFAP and NfL levels were only modestly affected by processing delay and freeze-thaw cycles. Plasma p-tau-181 levels notably increased with a 24-, 48-, and 72-h processing delay, but remained stable in serum. Intra-individual variation over two weeks was minimal for all biomarkers and their levels were substantially lower in serum when compared with plasma.
These results suggest that standardizing preanalytical variables will allow robust measurements of biomarkers of neuropathology in population studies.
样本采集和分析前方案可能会显著影响包含神经病理学血液生物标志物的大规模流行病学研究的结果。
评估几种神经病理学血液生物标志物在常见分析前条件下的稳定性和分析变异性。
我们从 41 名参与者中采集血清和血浆样本，并评估了在 4°C 下储存时长达 72 小时的处理延迟、三个冻融循环以及在 4°C 下储存时长达 48 小时的处理延迟与三个冻融循环的组合对生物标志物稳定性的影响。使用 Simoa 分析（Quanterix Inc.），我们测量了淀粉样蛋白-β 40（Aβ40）、淀粉样蛋白-β 42（Aβ42）、神经丝轻链（NfL）、胶质纤维酸性蛋白（GFAP）和磷酸化 tau 181（p-tau-181）。
我们发现，在血浆和血清样本中，24 小时的处理延迟后 Aβ40 和 Aβ42 水平显著下降，且单个冻融循环也会降低（p<0.0001）。然而，血清 Aβ42/40 比值在 48 小时的处理延迟内保持稳定，而血浆 Aβ42/40 比值在 72 小时的处理延迟内仅略有增加但具有统计学意义。处理延迟和冻融循环仅对血浆和血清中的 GFAP 和 NfL 水平有适度影响。血浆 p-tau-181 水平在 24、48 和 72 小时的处理延迟后显著增加，但在血清中保持稳定。所有生物标志物的个体内两周内的变异均较小，且与血浆相比，其水平在血清中显著降低。
这些结果表明，标准化分析前变量将允许在人群研究中对神经病理学生物标志物进行稳健的测量。
