These include glial fibrillary acidic protein (GFAP; a glial neuroinflammatory biomarker), neurofilament light chain (NfL; a neuroaxonal damage biomarker), phosphorylated tau181 (p‐tau181; a phospho‐tau isoform considered specific to Alzheimer's disease [AD] pathology), and the ratio of Aβ 42 to Aβ 40 (Aβ42/40; a marker of amyloid plaque deposition also considered specific to AD pathology; see Hansson et al.4 Here, GFAP is linked to early-onset autosomal dominant Alzheimer disease.