Purpose of review: The importance of biomarkers of Alzheimer's disease is increasing. The present review aims to offer a general view of plasma biomarkers of Alzheimer's disease and to discuss their relevance and limitations.
Recent findings: The broad overlap in the plasma amyloid β protein (Aβ) levels between patients with Alzheimer's disease and control individuals indicates that the plasma Aβ level cannot differentiate cases of sporadic Alzheimer's disease from control cases. Although the significance of Aβ for diagnosing Alzheimer's disease is controversial, high plasma concentrations of Aβ40 and low plasma concentrations of Aβ42 indicate an increased risk of dementia.
Summary: The usefulness of biomarkers in cerebrospinal fluid has been shown by numerous studies; this test is not commonly used, however, and blood biomarkers are therefore preferred. Increasing evidence shows that the plasma Aβ concentration may be a premorbid marker for the risk of Alzheimer's disease. It may be used for therapeutic monitoring, diagnosis of Aβ deposition in the brain, and also as a surrogate genetic marker to identify novel genetic determinants of Alzheimer's disease. A potential role of plasma Aβ concentration as a marker of incipient dementia warrants further investigation.