MAPT and tauopathy: Cerebrospinal fluid (CSF) amyloid-beta 42 (Aβ42), Aβ40, Aβ42/Aβ40 ratio, threonine-181-phosphorylated-tau (p-tau), and total-tau (t-tau) are reliable biomarkers for amyloidosis (A), tauopathy (T), and neurodegeneration (N).