Plasma pTau‐217 and NfL concentrations across diagnoses in an unselected memory clinic cohort

Abstract

AbstractBackgroundAlzheimer’s Disease (AD) plasma biomarkers have been proposed for amyloid positivity identification and for differentiating between diagnoses. Phosphorylated Tau‐217 (pTau‐217) has demonstrated good predictive ability for AD vs healthy controls. Neurofilament Light chain (NfL) differentiates between Frontotemporal Dementia (FTD) and other dementia. These factors have not be extensively tested in real‐world cohorts. The aim of this study was to investigate how pTau‐217 and NfL concentrations differ across clinical diagnoses in an unselected, real‐world memory clinic cohort.MethodWe included 418 consecutive patients from the Amsterdam Dementia Cohort. Patients were split among 12 diagnoses, including SCD, Mild Cognitive Impairment (MCI), probable AD, Dementia with Lewy Bodies (DLB) and FTD (Table 1). pTau‐217 was measured using the novel AlzPath assay, while NfL was measured using the Quanterix Simoa assay. were used to classify patients as high or low for pTau‐217 and NfL levels. The pTau‐217 cutoff (0.58 pg/mL) was the Youden index cutoff derived from the present data, based on amyloid‐positive AD vs amyloid‐negative SCD diagnosis (n = 57), using amyloid status derived from cerebrospinal fluid or Amyloid positron emission tomography for classification. (18.2 pg/mL) was chosen based on the sample’s median age (64 years) and taking the value associated with the 90th percentile of normal NfL levels (NfL interface for physicians (shinyapps.io)).ResultpTau‐217 levels were highest in patients with AD and Primary Progressive Aphasia (PPA), and lowest in those with Vascular Dementia (VaD) and other neurological diagnosis (Figure 1). NfL levels were highest in patients with VaD and FTD, and lowest in SCD and psychiatric diagnoses. The cutoffs highlighted similar trends, with higher proportions patients with elevated pTau‐217 levels observed in possible and probable AD, MCI, and DLB. Higher proportions of patients with high NfL levels were observed in FTD, PPA, VaD, and possible AD (Figure 2).ConclusionpTau‐217 concentrations vary as expected across the different diagnoses, with highest concentrations in AD pathology diagnostic groups. The elevated levels observed in DLB and PPA could be due to underlying AD co‐pathology. Following previous results, NfL concentrations were highest in FTD and lowest in psychiatry and SCD.