The recent development of blood biomarkers that target principal pathological hallmarks of Alzheimer’s disease (AD), including amyloid beta (Aβ) and phosphorylated tau (p-tau), have offered diagnostic and prognostic opportunities that were not feasible using cerebrospinal fluid (CSF) or neuroimaging biomarkers1–5. This evidence concerns the gene MAPT and early-onset autosomal dominant Alzheimer disease.