NEFL and Alzheimer disease: We then applied the IP-MS quantitative method to measure specific CSF NfL species in a validation cohort of 81 Alzheimer’s disease and control samples (30 amyloid-positive, CDR > 0; 16 amyloid-positive, CDR = 0; 10 amyloid-negative, CDR > 0; 25 amyloid-negative, CDR = 0; Supplementary Table 1).