NEFL and Alzheimer disease: Considering specific ND subgroups that are the most common differential diagnoses, AD and bvFTD, plasma and CSF NfL had high diagnostic performance for all ages (AD vs. PPD AUCs: 0.89 [plasma] and 0.95 [CSF]; bvFTD vs. PPD AUCs: 0.79 [plasma], 0.86 [CSF]), with even stronger performance in younger people (full details in Table 2).