Indicators of rapid cognitive decline in amnestic mild cognitive impairment: The role of plasma biomarkers using magnetically labeled immunoassays

Plasma levels of biomarkers change with the progression of Alzheimer's disease (AD), which involves the accumulation of pathological amyloid beta (A beta) and Tau protein tangles. However, few studies have investigated the association between plasma biomarkers and rapid cognitive decline in patients with amnestic mild cognitive impairment (aMCI) and AD. A total of 10 healthy controls, 24 patients with aMCI, and 19 patients with AD were enrolled. All participants underwent twice Mini-Mental State Examination (MMSE), with a mean 1.2 year interval. Immunomagnetic reduction was utilized to evaluate levels of plasma biomarkers, including amyloid beta 1-40 (A beta(1-40)), A beta(1-)(42), total Tau protein, phosphorylated Tau protein (Threonine 181), and alpha-synuclein (alpha-Syn). The correlations between plasma levels of biomarkers and MMSE change were examined. Our analysis reveals that current higher plasma levels of A beta(1-42) and alpha-Syn with the cut-off value of plasma A beta(1-42) > 17.26 pg/mL and alpha-Syn > 105 fg/mL had a moderate-to-high discriminatory capacity (area under the curve > 0.70) for identifying cognitive deterioration in patients with aMCI. Our results thus suggest that plasma levels of A beta(1-42) and alpha-Syn may be considered as useful markers to assess the severity of global cognitive decline in patients with aMCI.