Measurement of amyloid beta in nasal secretions as a potential biomarker for Alzheimer’s disease

Abstract

AbstractBackgroundWe investigated the level of amyloid beta (Aβ) in nasal secretions of patients with Alzheimer’s disease using multichannel impedance analyzer (ToAD) and electrical‐immunosorbent assay (El‐ISA), and determined the predictive value of Aβ in nasal secretions for AD diagnosis.MethodNasal secretions were obtained from 84 participants with probable AD dementia (ADD), 83 with amnestic mild cognitive impairment (MCI), 22 with cognitive decline associated with other neurological disorders (OND), and 62 cognitively unimpaired (CU) participants. Aβ oligomers in nasal secretions were analyzed using ToAD / El‐ISA analytical systems. Capture antibodies in El‐ISA kits specifically capture Aβ oligomer in nasal secretion, and then detection probes for El‐ISA method bind with amyloid beta oligomer sequentially. Finally, unbound free detection probes in solution was electrochemically measured by ToAD analyzer for quantifying Aβ oligomers. Because this analytical method is based on the back‐titration, the change of electrical signal is inversely proportional with the concentration of detectable Aβ oligomers. Electrical signals finally expressed to Cantis AD Index (CAI, 0∼99) which normalized by standards for system calibration.ResultThe CAI was higher in the probable ADD group than in the CU group (p < 0.05). The accuracy of the CAI was fair in separating into the probable ADD and CU groups (AUC of the ROC curve = 0.665, 95% CI = 0.572‐0.758, SE = 0.047, p = 0.001). The accuracy of the CAI was fair in separating into the participants with positive amyloid PET scan and those with negative amyloid PET scan (area under curve [AUC] of the receiver operating characteristic [ROC] curve = 0.697, 95% confidence interval [CI] = 0.629‐0.766, SE = 0.035, p < 0.001). The CAI has a negative correlation with Mini‐Mental State Examination score and positive correlations with Clinical Dementia Rating scale‐Sum of Boxes and amyloid PET centiloid scale scores.ConclusionThese results demonstrate that the level of Aβ in nasal secretions increases in AD and the detection of Aβ in nasal secretions using ToAD / El‐ISA analytical systems may be possible in predicting ADD.