Frontotemporal dementia is the leading cause of “true” A？/T+ profiles defined with Aβ42/40 ratio

Patients with positive tauopathy but negative Aβ42 (A？T+) in the cerebrospinal fluid (CSF) represent a diagnostic challenge. The Aβ42/40 ratio supersedes Aβ42 and reintegrates “false” A？T+ patients into the Alzheimer's disease spectrum. However, the biomarker and clinical characteristics of “true” and “false” A？T+ patients remain elusive