This is followed by the MCI phase, which is characterized by Aβ42 and enhanced levels of tTau and p-Tau-181; meanwhile, high levels or ratios of p-Tau-181/tTau, Aβ42, Aβ42/Aβ40, and tTau/Aβ42 are seen in the mild and moderate AD phases. Here, MAPT is linked to Alzheimer disease.