Detection of amyloid-beta and tau in tear fluid of patients with Alzheimer’s disease

Background There is growing interest in finding non-invasive alternatives to cerebrospinal fluid (CSF) that could serve as front-line diagnostics for Alzheimer’s disease (AD). In this study, we investigated AD-specific biomarkers in tear fluid.Methods Tear fluid was collected from 25 patients with subjective cognitive decline SCD), 24 patients with mild cognitive impairment (MCI), 11 dementia patients and nine controls. Amyloid-beta peptides (AB38, AB40, AB42), t-tau and p-tau levels in tear fluid were determined using multiplex immunoassays.Results Tear t-tau levels in dementia, MCI and SCD patients were higher than in HC (p = 0.002, p = 0.002 and p = 0.013, respectively). A negative correlation between AB42 and t-tau was found in both tear fluid and CSF. Levels of tear p-tau were detectable in patients but not in HC.Conclusions This study shows for the first time presence of amyloid-beta peptides (AB38, AB40, AB42), t-tau and p-tau in tear fluid.