Towards clinical implementation: Establishing standardized operating procedures to limit the pre‐analytical sample handling effects on the novel Alzheimer’s disease blood‐based biomarkers

Background Clinical implementation of novel blood‐based biomarkers for Alzheimer’s disease (AD) will aid in accurate, less‐invasive diagnosis. However, variation in blood handling may affect the accuracy of biomarker’s measurement. Establishing standardized operating procedures (SOPs) to mitigate these effects is essential for implementing novel blood‐based biomarkers into clinical use. We aim to provide an evidence‐based SOP specific for AD blood‐based biomarkers by studying the effects of multiple pre‐analytical variations in blood samples from AD and healthy controls (HCs). Here, we show the first results obtained, addressing the effect of biomarker’s adsorption to lab plastics, during sample processing. Method Blood samples are being withdrawn from 150 volunteers (AD and HCs) and treated according to one of ten pre‐analytical experimental protocols. Several aliquots per sample are being obtained, to be shared and analyzed among labs, focusing on labs with novel P‐tau plasma tests. Preliminary results are acquired for the effect of 1x, 2x and 4x tube transfers in fresh polypropylene tubes with fresh pipet tips at every transfer, compared to no tube transfer, as a reference condition. Sample analysis was performed on Simoa using the Simoa neurology 4‐plex E assay (Aβ 1‐42 , Aβ 1‐40 , GFAP, NfL), and the P‐tau181 V2 assay. A variation in the median value of one of the measured biomarkers of at least 10% from the reference condition was regarded as a significant change. Result Formally, medians of all tube transfers for all biomarkers measured (Aβ 1‐42 , Aβ 1‐40 , GFAP, NfL and Ptau‐181), stayed within the predefined range, for both AD and HC. However, the levels of Aβ 1‐42 and Aβ 1‐40 showed an obvious tendency to decrease at the 4 th tube transfer. For Aβ 1‐40 , levels in HCs were more affected compared to those in AD (median 92%; AD: median = 95%). For Aβ 1‐42 , both AD and HCs showed a similar decrease (median: 91% and 93%). This decrease is not so apparent with the Aβ 1‐42 /Aβ 1‐40 ratio . Conclusion In line with the results, 4 tube transfers or less should have no influence on the accuracy of the measured biomarkers. For Aβ peptide measurements, using the Aβ 1‐42 /Aβ 1‐40 ratio appears to stabilize the effect of tube transfer.