MAPT and Alzheimer disease: Recent evidence has suggested that plasma biomarkers, including amyloid-β (Aβ) 42, Aβ40, and p-tau181, may be a reliable alternative to CSF measures.8,9 Plasma markers, such as Aβ42, Aβ40, p-tau181, and neurofilament light (NFL), have had promising performances in detecting AD, and such assay development may make it possible to classify individuals based on related indicators of amyloidosis (A), tauopathy (T), and neurodegeneration (N); ie, the AT(N) categories.10,11,12,13,14,15,16 Whether the racial disparities reported in CSF total tau and p-tau181 extend to the plasma measures is unclear.