GFAP and Alzheimer disease: Several studies demonstrate that plasma biomarkers of AD pathology (e.g., Aβ42/40, phosphorylated tau [pTau-181]), astrogliosis (glial fibrillary acidic protein [GFAP]), and to a lesser extent, neuronal injury (neurofilament light chain [NfL]) relate to – and can be used to predict – cortical Aβ and tau burden [3–6].