Cerebrospinal fluid (CSF) neurofilament light chain
protein (NfL) and
Alzheimer's disease (AD) core
biomarker levels have been evaluated in cohorts of patients with
frontotemporal dementia spectrum (FTD), but the distribution of values across the different clinical syndromes and underlying
proteinopathies, and the relative diagnostic accuracy appear discordant among studies. We measured CSF NfL, total (t)-tau, phosphorylated (p)-tau, and
amyloid-β (Aβ)42 in healthy controls (n = 38) and subjects with a clinical, genetic, CSF
biomarker-based, and/or neuropathological diagnosis of FTD (n = 141) or AD (n = 60). Sub-analyses were conducted in a proportion of subjects with definite and/or probable
frontotemporal lobar degeneration with tau (
FTLD-TAU) (n = 42) or TDP43 pathology (
FTLD-TDP) (n = 36). Both FTD and AD groups showed significantly increased CSF NfL levels in comparison to controls (p < 0.001). CSF NfL levels were significantly higher in FTD patients than in AD (p < 0.001), reaching the highest values in
amyotrophic lateral sclerosis associated with FTD. Patients with probable and definite
FTLD-TDP had significantly higher NfL levels (p < 0.001) and lower p-tau/t-tau values (p < 0.001) in comparison with probable and definite
FTLD-TAU cases. NfL showed good diagnostic accuracy in the distinction between FTD and controls (AUC 0.862±0.027) and yielded an accuracy (AUC 0.861±0.045) comparable to that of the p-tau/t-tau ratio (AUC 0.814±0.050), with 80.0% sensitivity and 81.0% specificity, in the discrimination between probable/definite
FTLD-TAU and
FTLD-TDP. Our data further validate CSF NfL as a surrogate
biomarker of neurodegeneration and disease severity in patients with FTD spectrum. Moreover, they demonstrate a good diagnostic value for NfL and p-tau/t-tau ratio in the discrimination between
FTLD-TAU and
FTLD-TDP.