Eight-Year Longitudinal Study on the Assay Stability of Plasma Amyloid Beta 1-42 Peptide and Total Tau Protein Using Immunomagnetic Reduction.

The assay of plasma biomarkers plays a role in the assessment of Alzheimer's disease (AD) and the monitoring of treatments. One of the ultra-sensitive assay technologies is the so-called immunomagnetic reduction (IMR). According to published papers, plasma amyloid β peptide (Aβ) and total tau protein (T-Tau) are crucial biomarkers. From a practical point of view, it is necessary to monitor the longitudinal assay results in individuals frequently. Hence, it is essential to investigate the time-course measured concentrations of Aβ and T-Tau in control samples using IMR. In this work, the time-course measured concentrations of the control samples (Aβ: 20 pg/ml; T-Tau: 50 pg/ml) in IMR from 2016 to 2024 are analyzed. In addition to control samples, the reported levels of Aβ and T-Tau in human plasma from 2016 to 2024 assayed with IMR in cognitively normal subjects are inspected. The results show that the slopes of the year-dependent measured concentrations of Aβ and T-Tau in control samples over the 8 years do not significantly deviate from zero (p > 0.05). The insignificant drift in the reported Aβ and T-Tau concentrations in human plasma over the 8 years is also found (p > 0.05). These results reveal high consistencies in measured Aβ and T-Tau concentrations from time to time using IMR.