MAPT and Alzheimer disease: There are now well-validated blood biomarkers for Aβ and tau pathology, as well as neurodegeneration and astrocytic activation in AD, including Aβ40, Aβ42, glial fibrillary acidic protein (GFAP), neurofilament light chain (NfL) and P-tau181 as well as the ratio Aβ42/Aβ40 [60, 62, 63].