Plasma phospho-tau181 increases with Alzheimer's disease clinical severity and is associated with tau- and amyloid-positron emission tomography

Introduction: We examined and compared plasma phospho-tau181 (pTau181) and total tau: (1) across the Alzheimer's disease (AD) clinical spectrum; (2) in relation to brain amyloid beta (A beta) positron emission tomography (PET), tau PET, and cortical thickness; and (3) as a screening tool for elevated brain AO. Methods: Participants included 172 cognitively unimpaired, 57 mild cognitively impaired, and 40 AD dementia patients with concurrent A beta PET (Pittsburgh compound B), tau PET (AV1451), magnetic resonance imaging, plasma total tau, and pTau181. Results: Plasma total tau and pTau181 levels were higher in AD dementia patients than those in cognitively unimpaired. Plasma pTau181 was more strongly associated with both A beta and tau PET. Plasma pTau181 was a more sensitive and specific predictor of elevated brain A beta than total tau and was as good as, or better than, the combination of age and apolipoprotein E (APOE). Discussion: Plasma pTau181 may have utility as a biomarker of AD pathophysiology and as a noninvasive screener for elevated brain A beta. (C) 2018 the Alzheimer's Association. Published by Elsevier Inc. All rights reserved.