NEFL and Alzheimer disease: It has been extensively explored in the context of AD, where plasma GFAP levels increase in the preclinical phase and may serve as an early biomarker for dementia prediction.34, 35, 36, 37, 38, 39 Notably, GFAP alterations occur before changes in plasma p-tau or NfL in AD37 and it may link Aβ with initial tau pathology in AD, making it a valuable marker in AD progression.35