Fig. 2

Contrasting methods to measure plasma Aβ. Two common methods to measure plasma Aβ are IP-MS assays (left) and immunoassays (right). In IP-MS assays, the detector measures Aβ species directly and quantitation is performed with an internal standard of stable isotope-labeled Aβ. In immunoassays, Aβ species are measured indirectly with antibody binding, and a different detection antibody must be used for each Aβ isoform. Immunoassays perform quantitation with an external standard. The immunoassay depicted in this figure is a plate-based sandwich immunoassay; bead-based immunoassays are also common, using fluorescently barcoded beads bound to an antibody for indirect measuring of a target. Figure created with BioRender.com