MAPT and Alzheimer disease: According to the present results, plasma P-tau217 could serve as a tool in clinical trials for (1) selection of individuals with preclinical AD who harbor early stage tau pathology before insoluble tau aggregates are prevalent and detectable by tau-PET and (2) monitoring target engagement of certain anti-tau drugs (given that these drugs do not interfere with the assay performance) and downstream pharmacodynamic effects on tau pathology by both anti-amyloid and anti-tau treatments.