INTRODUCTION: Diagnostic relevance of plasma amyloid β (Aβ) for Alzheimer's disease (AD) process yields conflicting results. The objective of the study was to assess plasma levels of Aβ and Aβ in amnestic mild cognitive impairment (MCI), nonamnestic MCI, and AD patients and to investigate relationships between peripheral and central biomarkers.
METHODS: One thousand forty participants (417 amnestic MCI, 122 nonamnestic MCI, and 501 AD) from the Biomarker of AmyLoïd pepTide and AlZheimer's diseAse Risk multicenter prospective study with cognition, plasma, cerebrospinal fluid (CSF), and magnetic resonance imaging assessments were included.
RESULTS: Plasma Aβ and Aβ were lower in AD (36.9 [11.7] and 263  pg/mL) than in amnestic MCI (38.2 [11.9] and 269  pg/mL) than in nonamnestic MCI (39.7 [10.5] and 272  pg/mL), respectively (P = .01 for overall difference between groups for Aβ and P = .04 for Aβ). Globally, plasma Aβ correlated with age, Mini-Mental State Examination, and APOE ε4 allele. Plasma Aβ correlated with all CSF biomarkers in MCI but only with CSF Aβ in AD.
DISCUSSION: Plasma Aβ was associated with cognitive status and CSF biomarkers, suggesting the interest of plasma amyloid biomarkers for diagnosis purpose.