MAPT and Alzheimer disease: We identified six main predictive objectives from the included studies: (1) classifying the stages of AD (SCD versus MCI versus AD dementia), (2) detecting the presence of amyloid, tau, or neurodegeneration, (3) differentiating AD dementia from other types of dementia, (4) predicting SCD conversion to MCI or AD dementia, (5) predicting MCI conversion to AD dementia, and (6) predicting the rate of cognitive decline (Table 1).