Plasma amyloid assay as a pre-screening tool for amyloid positron emission tomography imaging in early stage Alzheimer’s disease

Abstract

IntroductionDue to the high cost and high failure rate of ascertaining amyloid positron emission tomography positivity (PET+) in patients with earlier stage Alzheimer’s disease (AD), an effective pre-screening tool for amyloid PET scans is needed.MethodsPatients with mild cognitive impairment (n\u2009=\u200933, 24.2% PET+, 42% females, age 74.4\u2009±\u20097.5, MMSE 26.8\u2009±\u20091.9) and mild dementia (n\u2009=\u200919, 63.6% PET+, 36.3% females, age 73.0\u2009±\u20099.3, MMSE 22.6\u2009±\u20092.0) were recruited. Amyloid PET imaging, Apolipoprotein E (APOE) genotyping, and plasma amyloid β (Aβ)1–40, Aβ1–42, and total tau protein quantification by immunomagnetic reduction (IMR) method\xa0were performed. Receiver operating characteristics (ROC) analysis and Youden’s index\xa0were performed to identify possible cut-off points, clinical sensitivities/specificities, and areas under the curve (AUCs).ResultsAmyloid PET+ participants had lower plasma Aβ1–42 levels than amyloid PET-negative (PET−) subjects. APOE ε4 carriers had higher plasma Aβ1–42 than non-carriers. We developed an algorithm involving the combination of plasma Aβ1–42 and APOE genotyping. The success rate for detecting amyloid PET+ patients effectively increased from 42.3 to 70.4% among clinically suspected MCI and mild dementia patients.ConclusionsOur results demonstrate the possibility of utilizing APOE genotypes in combination with plasma Aβ1–42 levels as a pre-screening tool for predicting the positivity of amyloid PET findings in early\xa0stage dementia patients.