Plasma P‐tau181 to Aβ42 ratio is associated with brain amyloid burden and hippocampal atrophy in an Asian cohort of Alzheimer's disease patients with concomitant cerebrovascular disease

Abstract Introduction There is increasing evidence that phosphorylated tau (P‐tau181) is a specific biomarker for Alzheimer's disease (AD) pathology, but its potential utility in non‐White patient cohorts and patients with concomitant cerebrovascular disease (CeVD) is unknown. Methods Single molecule array (Simoa) measurements of plasma P‐tau181, total tau, amyloid beta (Aβ)40 and Aβ42, as well as derived ratios were correlated with neuroimaging modalities indicating brain amyloid (Aβ+), hippocampal atrophy, and CeVD in a Singapore‐based cohort of non‐cognitively impaired (NCI; n = 43), cognitively impaired no dementia (CIND; n = 91), AD ( n = 44), and vascular dementia (VaD; n = 22) subjects. Results P‐tau181/Aβ42 ratio showed the highest area under the curve (AUC) for Aβ+ (AUC = 0.889) and for discriminating between AD Aβ+ and VaD Aβ− subjects (AUC = 0.903). In addition, P‐tau181/Aβ42 ratio was associated with hippocampal atrophy. None of the biomarkers was associated with CeVD. Discussion Plasma P‐tau181/Aβ42 ratio may be a noninvasive means of identifying AD with elevated brain amyloid in populations with concomitant CeVD.