Blood p-tau is a highly specific pathological blood biomarker for AD pathology and encompasses all diagnostic capabilities of CSF p-tau (Benussi et al., 2020; Karikari et al.,2020a,b; Lantero Rodriguez et al., 2020; Moscoso et al., 2020; O’Connor et al., 2020; Ashton et al., 2021). This evidence concerns the gene MAPT and Alzheimer disease.