Beta-Amyloid 42 (Aβ42), Plasma

Beta-amyloid 1-42 (Aβ42) is the amyloid peptide that aggregates into the plaques characteristic of Alzheimer's disease. As plaques accumulate in the brain, the amount of Aβ42 circulating in blood tends to fall. Plasma Aβ42 is interpreted together with p-tau217 through the p-tau217/beta-amyloid 42 ratio rather than as a standalone value.