Biomarker evidence for amyloid-β (Aβ) and tau pathology is now used for a diagnosis of AD, 2 and a prerequisite for (inclusion in trials of) disease-modifying treatments.3 - 5 However, within individuals with AD there is biological heterogeneity and variability in disease progression, which makes interpreting trial results and prognostication on an individual level difficult.6,7. This evidence concerns the gene MAPT and Alzheimer disease.