Diagnostic impact of tau versus amyloid PET in patients with cognitive symptoms

The diagnostic efficacy of tau positron emission tomography (PET) relative to amyloid PET in memory clinic settings remains underexplored. In this study, 1008 consecutive Han Chinese individuals with cognitive impairments were recruited between March 2020 and July 2025. They underwent comprehensive clinical assessment, amyloid PET, and tau PET. Diagnostic reclassification, accuracy, and changes in diagnostic confidence were evaluated across cognitive stages and etiologic categories. For Alzheimer's disease (AD) diagnosis, tau PET demonstrated high sensitivity (97.8%) and specificity (95.4%), showing substantial agreement with amyloid PET. Moreover, tau PET provided additional information beyond that offered by amyloid PET alone. In patients clinically diagnosed with non-AD disorders, tau PET led to a significantly higher rate of diagnostic change compared with amyloid PET (p = 0.018). After a diagnosis based on amyloid PET results, the subsequent addition of tau PET information still resulted in a diagnostic change in 10.0% of patients, highlighting its incremental value. Furthermore, tau PET significantly improved diagnostic confidence (from 68.6% to 84.2%), and the confidence gained from tau PET was significantly greater than that from amyloid PET alone within non-AD diseases. Our findings suggest tau PET offers diagnostic performance for AD comparable to that of amyloid PET, while providing additional value in detecting non-AD tauopathies and clarifying complex cases. These observations support the potential for tau PET to complement existing diagnostic workflows in memory clinic settings.