MAPT and Alzheimer disease: p-tau181 differentiating: 1. Cohort 1 - AD vs. FTLD (n = 190): AuROC = 0.89 with clinical diagnosis as reference; - Aβ-PET + vs.-: AuROC = 0.86 with amyloid-PET as reference; - autopsy-confirmed AD (n = 15) vs. FTLD-tau (n = 52) AuROC = 0.86 with neuropathology as reference