Cerebrospinal Fluid Neurofilament Light Chain and Soluble Amyloid Precursor Protein - β in the Subcortical Small Vessel Type of Dementia

Abstract

Introduction: The subcortical small vessel type of dementia (SSVD) is a common form of vascular dementia. There is a lack of disease-specific cerebrospinal fluid (CSF) biomarkers. We investigated whether CSF concentrations of neurofilament light chain (NFL), soluble amyloid precursor protein-α (sAPP-α), sAPP-β, and CSF/serum albumin ratio could separate SSVD from healthy controls, Alzheimer's disease (AD) and mixed dementia (combined AD and SSVD). Methods: Patients with SSVD (n = 38), AD (n = 121), mixed dementia (n = 62), and healthy controls (n = 96) were included. The CSF biomarkers were measured using immunoassays, and their independent contribution to the separation between groups were evaluated using the Wald test. Then, the area under the receiver operating characteristics curve (AUROC) and 95% confidence intervals (CIs) were calculated. Results: Elevated NFL concentrations and decreased sAPP-β concentrations independently separated SSVD from controls, and sAPP-β also distinguished SSVD from AD and mixed dementia. Furthermore, the combination of NFL and sAPP-β discriminated SSVD from controls with high accuracy (AUROC 0.903, 95% CI: 0.834 – 0.972). Additionally, sAPP-β combined with the core AD biomarkers (β-amyloid1-42, total tau, and phosphorylated tau181) had a high ability to separate SSVD from AD (AUROC 0.886, 95% CI: 0.830 – 0.942) and mixed dementia (AUROC 0.903, 95% CI: 0.838 – 0.968). Discussion: The high accuracy of NFL and sAPP-β to separate SSVD from controls supports that SSVD is a specific diagnostic entity. Moreover, sAPP-β in combination with the core AD biomarkers distinguished SSVD from AD and mixed dementia.