The following findings can be used to diagnose AD: amyloid PET; CSF Aβ 42/40, CSF p-tau 181/Aβ 42, CSF t-tau/Aβ 42; or “accurate” plasma assays, where “accurate” can be defined as approved CSF assays in detecting abnormal amyloid PET in the intended-use population. Here, MAPT is linked to Alzheimer disease.