MAPT and Alzheimer disease: Later in 2018, the biomarker-based A-T-N (Amyloid/Tau/Neurodegeneration) research framework for AD was established indicating that biomarkers are necessary to support an in vivo diagnosis of AD, especially in the preclinical and prodromal phases of the disease when clinical symptoms are either absent or very subtle, but neuropathological changes are already ongoing and detectable [4].