A research team at Keio University has demonstrated that the plasma biomarker amyloid β (Aβ) 42/40 ratio can predict Aβ deposition in the brain with high accuracy, as measured by using positron emission tomography (PET). The team was led by Project Associate Professor Shogyoku Bun and Project Professor Daisuke Ito of the Keio University School of Medicine. The results of this study were published in the medical journal Alzheimer's Research & Therapy.
Owing to the high cost of amyloid PET and the invasiveness of cerebrospinal fluid testing, alternative methods to measure Aβ using plasma biomarkers have been developed. However, these methods have not been applied in clinical settings as they also have high costs.
In this study, the research team measured plasma Aβ1-42 and Aβ1-40 levels in healthy volunteers and patients with various types of dementia using a fully automated immunoassay and investigated whether the plasma Aβ42/40 ratio could predict amyloid PET positivity.
The results showed that the plasma Aβ42/40 ratio predicted amyloid PET positivity with exceedingly high accuracy, with an area under the curve (AUC) value of 0.95 (the closer the value is to 1, the higher the accuracy). The prediction accuracy was significantly higher than that of other promising plasma biomarkers. The Aβ42/40 ratio further predicted early amyloid accumulation with high accuracy.
The findings indicated that a simple blood test can be used to accurately screen a wide range of patients for Aβ deposition in the brain, which is a key pathological feature of Alzheimer's-type dementia. The fully automated immunoassay used in this study is also used for COVID-19 antigen and antibody testing, showing potential for further application as a novel testing method.
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