Advantages and disadvantages of the use of the CSF Amyloid β (Aβ) 42/40 ratio in the diagnosis of Alzheimer's Disease

Alzheimers Res Ther. 2019 Apr 22;11(1):34. doi: 10.1186/s13195-019-0485-0.


The cerebrospinal fluid (CSF) biochemical markers (biomarkers) Amyloidβ 42 (Aβ42), total Tau (T-tau) and Tau phosphorylated at threonine 181 (P-tau181) have proven diagnostic accuracy for mild cognitive impairment and dementia due to Alzheimer's Disease (AD). In an effort to improve the accuracy of an AD diagnosis, it is important to be able to distinguish between AD and other types of dementia (non-AD). The concentration ratio of Aβ42 to Aβ40 (Aβ42/40 Ratio) has been suggested to be superior to the concentration of Aβ42 alone when identifying patients with AD. This article reviews the available evidence on the use of the CSF Aβ42/40 ratio in the diagnosis of AD. Based on the body of evidence presented herein, it is the conclusion of the current working group that the CSF Aβ42/40 ratio, rather than the absolute value of CSF Aβ42, should be used when analysing CSF AD biomarkers to improve the percentage of appropriately diagnosed patients.

Keywords: Alzheimer’s Disease; Amyloidβ Peptides; Aβ42/40 ratio; Biomarkers; Cerebrospinal Fluid.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Alzheimer Disease / cerebrospinal fluid*
  • Amyloid beta-Peptides / cerebrospinal fluid*
  • Biomarkers / cerebrospinal fluid
  • Humans
  • Peptide Fragments / cerebrospinal fluid*


  • Amyloid beta-Peptides
  • Biomarkers
  • Peptide Fragments
  • amyloid beta-protein (1-40)
  • amyloid beta-protein (1-42)