NEFL and Alzheimer disease: Plasma tau phosphorylated at residue 217 (p-tau217) has demonstrated high accuracy in detecting AD pathology9–11, with strong associations with CSF and PET biomarkers of AD12, 13, while other biomarkers, particularly neurofilament light protein (NfL), a marker of neurodegeneration, and glial fibrillary acidic protein (GFAP), an astrocytic reactivity marker, provide important complementary information and a more comprehensive assessment of disease pathology14, 15.