MAPT and Alzheimer disease: Aβ 1-42 dosage is one of the three biological markers indicative of an AD diagnosis: Aβ 1-42 is decreased in the cerebrospinal fluid (CSF) of AD patients, whereas total Tau and phosphorylated Tau levels are increased (Blennow and Hampel, 2003; Herukka et al., 2005; Bombois et al., 2013).