MAPT and Alzheimer disease: The coexistence of CSF decreased β-amyloid1-42/β-amyloid1-40 (Aβ42/Aβ40) ratio and elevated phosphorylated tau at threonine-181 (p-tau), which reflect amyloidosis and tauopathy respectively, allows to claim the presence of AD-related neurobiology, regardless to cognitive stage and clinical presentation [210].