A Review of Application of Aβ42/40 Ratio in Diagnosis and Prognosis of Alzheimer's Disease

The number of patients with Alzheimer's disease (AD) and non-Alzheimer's disease (non-AD) has drastically increased over recent decades. The amyloid cascade hypothesis attributes a vital role to amyloid-beta protein (A beta) in the pathogenesis of AD. As the main pathological hallmark of AD, amyloid plaques consist of merely the 42 and 40 amino acid variants of A beta (A beta(42) and A beta(40)). The cerebrospinal fluid (CSF) biomarker A beta(42/40) has been extensively investigated and eventually integrated into important diagnostic tools to support the clinical diagnosis of AD. With the development of highly sensitive assays and technologies, blood-based A beta(42/40), which was obtained using a minimally invasive and cost-effective method, has been proven to be abnormal in synchrony with CSF biomarker values. This paper presents the recent progress of the CSF A beta(42/40) ratio and plasma A beta(42/40) for AD as well as their potential clinical application as diagnostic markers or screening tools for dementia.