Clinical tools to differentiate behavioral variant frontotemporal dementia from phenocopies.

INTRODUCTION: Behavioral variant frontotemporal dementia (bvFTD) is often misdiagnosed, particularly in psychiatric phenocopies of the disease (phFTD). We compared the top-performing bvFTD-specific behavioral tools, identified in a prior systematic review, for differentiating bvFTD from phFTD. METHODS: In this prospective diagnostic accuracy study, consecutively recruited participants with suspected bvFTD by a specialist physician completed nine bvFTD-specific tools at baseline with a blinded assessor. Final diagnoses were assigned by multidisciplinary consensus after follow-up. Diagnostic performance was assessed using receiver operating characteristic analyses. RESULTS: Fifty-one participants were included (25 bvFTD, 26 phFTD). The Frontotemporal Dementia versus Primary Psychiatric Disorder (FTDvsPPD) checklist showed the best discrimination (area under the curve [AUC] 0.92), with 80.0% sensitivity and 96.2% specificity. The Social Behavior Observer Checklist (SBOC) performed next best (AUC 0.85). The Informant Based Questionnaire and Pick's Disease Scale showed moderate discrimination and other tools performed poorly. DISCUSSION: Tools focused on clinician observation outperformed informant-reliant measures. The FTDvsPPD checklist showed the strongest rule-in and rule-out utility, while the SBOC provided useful rule-in support.