MAPT and Alzheimer disease: In 1999, a first paper showed that MCI patients progressing to AD with dementia, which is sometimes called “converting,” during the clinical follow-up period had the typical AD CSF profile of high T-tau and P-tau together with low Aβ42, and levels were equally abnormal in the MCI and the dementia stage in cases with longitudinal sampling (Andreasen et al., 1999).