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J Prev Alzheimers Dis. 2019;6(1):34-41. doi: 10.14283/jpad.2018.41.

Plasma Aβ42/40 Ratio Detects Early Stages of Alzheimer's Disease and Correlates with CSF and Neuroimaging Biomarkers in the AB255 Study.

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Pedro Pesini, PhD. Vía Hispanidad 21, 50009 Zaragoza, Spain; Telephone number: +34 976 796 562; Fax: (+34) 976 217 802; Email:



Easily accessible biomarkers are needed for the early identification of individuals at risk of developing Alzheimer's disease (AD) in large population screening strategies.


This study evaluated the potential of plasma β-amyloid (Aβ) biomarkers in identifying early stages of AD and predicting cognitive decline over the following two years.


Total plasma Aβ42/40 ratio (TP42/40) was determined in 83 cognitively normal individuals (CN) and 145 subjects with amnestic mild cognitive impairment (a-MCI) stratified by an FDG-PET AD-risk pattern.


Significant lower TP42/40 ratio was found in a-MCI patients compared to CN. Moreover, a-MCIs with a high-risk FDG-PET pattern for AD showed even lower plasma ratio levels. Low TP42/40 at baseline increased the risk of progression to dementia by 70%. Furthermore, TP42/40 was inversely associated with neocortical amyloid deposition (measured with PiB-PET) and was concordant with the AD biomarker profile in cerebrospinal fluid (CSF).


TP42/40 demonstrated value in the identification of individuals suffering a-MCI, in the prediction of progression to dementia, and in the detection of underlying AD pathology revealed by FDG-PET, Amyloid-PET and CSF biomarkers, being, thus, consistently associated with all the well-established indicators of AD.


Alzheimer’s disease; Aβ ratio; biomarker; plasma; β-amyloid (Aβ)


Conflict of interest statement

VPG, PP, JR, ISJ, LS, IM and MS are employees of Araclon Biotech. All other co-authors do not have conflicts of interest related to this study.

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