NEFL and Alzheimer disease: The consistency between plasma biomarkers and PET-CT in detecting amyloid pathology was evaluated using Cohen's Kappa. Plasma Aβ42 levels and the Aβ42/Aβ40 ratio were significantly lower in AD patients compared to those with MCI and HC (p<0.05), while levels of p-tau181, p-tau217, NfL, and GFAP were significantly elevated (p<0.05).