Application of the AT(N) and Other CSF Classification Systems in Behavioral Variant Frontotemporal Dementia.

Abstract

Patients with a frontotemporal lobar degeneration (FTLD) usually manifest with behavioral variant frontotemporal dementia (bvFTD). Alzheimer's disease (AD) may also manifest with a predominant behavioral-dysexecutive syndrome, similar to bvFTD. Cerebrospinal fluid (CSF) biomarkers, such as total tau (τT), phosphorylated tau (τP-181) and amyloid beta with 42 amino-acids (Aβ42), can predict AD pathology in vivo. The aim of this study was to compare the τT/Aβ42 and τP-181/Aβ42 ratios, the BIOMARKAPD/ABSI criteria and the AT(N) classification system in a cohort of bvFTD patients. A total of 105 bvFTD patients (21 possible bvFTD; 20%) with CSF data, examined from 2008 to 2022, were included. Seventy-eight AD patients and 62 control subjects were included. The CSF biomarkers were measured with Innotest (2008-2017 subcohort) and EUROIMMUN (2017-2022 subcohort) ELISAs. Depending on the classification system, 7.6 to 28.6% of bvFTD had an AD biochemical profile. The τT/Aβ42 and τP-181/Aβ42 ratios classified more patients as AD compared to the BIOMARKAPD/ABSI and AT(N) systems. The patients with possible bvFTD had higher frequencies of AD compared to the probable bvFTD patients. The four classification criteria of CSF AD biomarkers resulted in differences in AD allocation in this bvFTD cohort. A consensus on the optimal classification criteria of CSF AD biomarkers is pivotal.