Development and Technical Validation of an Immunoassay for the Detection of APP (Aβ) in Biological Samples.

The ratio of amyloid precursor protein (APP) (Aβ)/Aβ in blood plasma was reported to represent a novel Alzheimer's disease biomarker. Here, we describe the characterization of two antibodies against the N-terminus of Aβ and the development and "fit-for-purpose" technical validation of a sandwich immunoassay for the measurement of Aβ. Antibody selectivity was assessed by capillary isoelectric focusing immunoassay, Western blot analysis, and immunohistochemistry.