MAPT and Alzheimer disease: Moreover, plasma cis P-tau is induced extremely early in AD patients (Ashton et al., 2021; Milà-Alomà et al., 2022; Shiravandi et al., 2022), being the first blood biomarker able to distinguish between Braak stage I/II in incipient AD from health controls (Ashton et al., 2021) and to reach the abnormal level with the lowest Aβ burden in pre-clinical AD patients (Milà-Alomà et al., 2022).