MAPT and amyloidosis: We examined (i) whether changes in plasma pTau217 levels over time track progression of Alzheimer’s disease proteinopathy ascertained from amyloid and tau positron emission tomography (PET) with [11C] -PiB for amyloid and [18F] MK-6240 for tau; (ii) whether plasma pTau217 levels accurately differentiate people with varying degrees of amyloid and tau burden; and (iii) whether plasma pTau217 levels are associated with longitudinal cognition.