Social cognition differentiates phenocopy syndrome of behavioural variant frontotemporal dementia from behavioural variant frontotemporal dementia

Background Patients displaying clinical features of behavioural variant of frontotemporal dementia (bvFTD) but lacking both neuroimaging abnormalities and clinical progression are considered to represent the phenocopy syndrome of bvFTD (phFTD). Extensive clinical overlap between early phase bvFTD and phFTD hampers diagnostic distinction. We aimed to assess the diagnostic value of clinician‐rated, self‐reported and caregiver‐reported symptoms for clinical distinction between phFTD and bvFTD. Methods There were 33 phFTD and 95 probable bvFTD patients included in the study (total N = 128). Clinician‐rated, self‐reported tests and caregiver‐reported symptoms were compared between phFTD and bvFTD on social cognition, behaviour, mood and activities of daily living (ADL). Scores were compared between groups, followed by multiple logistic regression analysis, adjusted for age and sex. Receiver operating characteristic curves were plotted to assess diagnostic value. Results Using clinician‐rated and self‐reported tests, phFTD patients performed better on facial emotion recognition and reported more depressive symptoms. Caregiver‐reported behavioural symptoms indicated higher behavioural and ADL impairment in phFTD compared to bvFTD. Facial emotion recognition provided highest diagnostic accuracy for distinction of phFTD from bvFTD (area under the curve (AUC) 0.813 95% CI 0.735–0.892, P