NEFL and Alzheimer disease: Serum neurofilament light chain (NfL) also may be useful for discriminating between lvPPA and non-lvPPA with 81% sensitivity and 67% specificity (22), and others have shown elevated NfL in svPPA and naPPA relative to a small number of lvPPA (25) [also see (31)], although others have found CSF NfL elevated in AD (32, 33).