MAPT and Alzheimer disease: Exploratory analyses of plasma samples using multidimensional protein assays will include established AD biomarkers, such as amyloid β 42 over 40 ratio (Aβ42/Aβ40), phosphorylated tau forms (181 and 217), neurofilament light as a neurodegeneration marker and glial fibrillar acidic protein (GFAP) as an astrocytic activation marker.24