Biomarkers with Plasma Amyloid β and Tau Protein Assayed by Immunomagnetic Reduction in Patients with Amnestic Mild Cognitive Impairment and Alzheimer's Disease.

This review addresses recent developments in the analyses of plasma amyloid beta (Aβ) and total tau (t-tau) protein levels as biomarkers for discriminating amnestic mild cognitive impairment (aMCI) from Alzheimer disease (AD), using immunomagnetic reduction (IMR). Recent studies have focused on the differential diagnosis of normal controls (NCs) with aMCI or AD. Results of 15 clinical studies have demonstrated decrease in plasma Aβ1-40 and increase in plasma Aβ1-42 and t-tau levels in patients with aMCI and AD. For a given biomarker, effect size is determined by comparing the mean ratios of biomarker levels between two diagnostic groups. Effect sizes are less than 1 for Aβ1-40 (0.606-1.032) but >1 for Aβ1-42 (1.018-2.167) and t-tau (1.030-4.147) in aMCI and AD compared with NCs. The effect size of the plasma tau significantly increases the most as aMCI progresses to AD. Studies into the application of IMR to determine plasma Aβ and tau levels as biomarkers for aMCI or AD have recently progressed. Future investigations should validate recently published results, preferably in patients with pathologically confirmed AD. In addition, effort should be directed toward standardizing the design of such studies and data analysis. Keywords: amyloid beta, plasma tau, Alzheimer disease, biomarker, mild cognitive impairment.