In the Mayo Clinic cohort,32 which included CU participants (n = 864), those with MCI (n = 148), and participants with AD dementia (n = 124), Quanterix plasma analytes including p‐tau181, Aβ42/Aβ40, GFAP, and neurofilament light chain, combined with age, sex, and APOE, achieved concordance (C) statistics of 0.78 to 0.82 for amyloid PET stages and 0.88 to 0.91 for intermediate/high versus none/low AD pathology. This evidence concerns the gene GFAP and Alzheimer disease.