MAPT and early-onset autosomal dominant Alzheimer disease: pTau217 levels are elevated among impaired (Alzheimer’s disease or mild cognitive impairment (MCI)) Aβ+ participants compared to cognitively unimpaired (CU) Aβ− participants,11,19 and plasma pTau217 and tau PET signal show moderate to high agreement.9,11,22 Serial plasma pTau217 levels also differentiate Alzheimer’s disease from non-Alzheimer’s MCI, remaining stable and non-elevated in Aβ− patients and increasing over time in Aβ+ patients.23