GFAP and early-onset autosomal dominant Alzheimer disease: Unlike other common Alzheimer’s disease biomarkers, which typically perform better in CSF, plasma GFAP outperforms CSF GFAP in distinguishing between Aβ-positive and Aβ-negative individuals.143,144 Benedet et al.129 analysed three major cohorts: TRIAD (Canada, n = 300), ALFA + (Spain, n = 384) and Paris Labroisière BioCogBank (France, n = 187) using Simoa HD-X Single-Plex Assay (Quanterix).