GFAP and Alzheimer disease: Blood‐based biomarkers (BBMs) have emerged as more accessible in vivo markers of AD/ADRD pathologies, including amyloid beta (Aβ)42/40 ratio,8, 9, 10 phosphorylated tau (p‐tau)181,11, 12, 13, 14 neurofilament light chain (NfL),15, 16, 17 and glial fibrillary acidic protein (GFAP).18, 19