MAPT and Alzheimer disease: The CSF levels of T-tau, P-Tau and Aβ42 or, even more specifically,the combination of low Aβ42 and high levels of T-tau and P-Tau,provide optimal sensitivity and specificity in the diagnosis of AD patients (even atMCI stage) against normal controls.51,52 The combinedanalysis of the CSF biomarkers, especially P-Tau/Aβ42 ratio, isalso useful for the differential diagnosis between AD and frontotemporal lobardegeneration, regardless of its behavioural (bvFTD) or semanticpresentation.11,31