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Alzheimers Dement (Amst). 2019 Jul 26;11:510-519. doi: 10.1016/j.dadm.2019.05.007. eCollection 2019 Dec.

Plasma amyloid beta levels are associated with cerebral amyloid and tau deposition.

Author information

1
Department of Radiology and Imaging Sciences, Center for Neuroimaging, Indiana University School of Medicine, Indianapolis, IN, USA.
2
Indiana Alzheimer Disease Center, Indiana University School of Medicine, Indianapolis, IN, USA.
3
Araclon Biotech S.L., Zaragoza, Spain.
4
Department of Neurology, Indiana University School of Medicine, Indianapolis, IN, USA.

Abstract

Introduction:

We investigated the relationship of plasma amyloid beta (Aβ) with cerebral deposition of Aβ and tau on positron emission tomography (PET).

Methods:

Forty-four participants (18 cognitively normal older adults [CN], 10 mild cognitive impairment, 16 Alzheimer's disease [AD]) underwent amyloid PET and a blood draw. Free and total plasma Aβ40 and Aβ42 were assessed using a validated assay. Thirty-seven participants (17 CN, 8 mild cognitive impairment, 12 AD) also underwent a [18F]flortaucipir scan. Scans were preprocessed by standard techniques, and mean global and regional amyloid and tau values were extracted. Free Aβ42/Aβ40 (Aβ F42:F40) and total Aβ42/Aβ40 (Aβ T42:T40) were evaluated for differences by diagnosis and relation to PET Aβ positivity. Relationships between these measures and cerebral Aβ and tau on both regional and voxel-wise basis were also evaluated.

Results:

Lower Aβ T42:T40 was associated with diagnosis and PET Aβ positivity. Lower plasma Aβ T42:T40 ratios predicted cerebral Aβ positivity, both across the full sample and in CN only. Finally, lower plasma Aβ T42:T40 ratios were associated with increased cortical Aβ and tau in AD-related regions on both regional and voxel-wise analyses.

Discussion:

Plasma Aβ measures may be useful biomarkers for predicting cerebral Aβ and tau. Additional studies in larger samples are warranted.

KEYWORDS:

Alzheimer's disease (AD); Amyloid positron emission tomography (PET); Blood biomarkers; Tau positron emission tomography (PET); mild cognitive impairment (MCI)

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