NEFL and Alzheimer disease: One study has demonstrated that NfL is increased in the serum of patients with primary progressive aphasia compared with controls and discriminates between nfPPA/svPPA and lvPPA with 81% sensitivity and 67% specificity [56]; while plasma concentrations of Aβ peptides and pTau may be more accurate in differentiating AD from other diagnoses, NfL has the potential to support the diagnosis of AD-related primary progressive aphasia, particularly lvPPA.