BACKGROUND: The well-established core biomarkers used to identify Alzheimer's disease (AD) overlap with other dementia disorders such as dementia with Lewy bodies (DLB) and Parkinson's disease with dementia (PDD). This study aimed to evaluate whether the cerebrospinal fluid (CSF) amyloid-β (Aβ)1-42/Aβ1-40 ratio, measured by a novel method, could improve the differential diagnosis of AD, DLB and PDD.

METHOD: CSF levels of Aβ1-40 and Aβ1-42 in patients with PDD, DLB, AD, Parkinson's disease and controls were analyzed using an amplified luminescent proximity homogenous immunoassay along with conventional immunoassays.

RESULTS: The CSF Aβ1-42/Aβ1-40 ratio increased discrimination of AD from PDD and DLB compared with either of the two Aβ biomarkers individually.

CONCLUSION: The use of the Aβ1-42/Aβ1-40 ratio could improve the differentiation of AD from PDD and DLB.