Salivary biomarkers in Alzheimer's disease

Abstract

Objectives: The objective of this study was to evaluate the changes that can occur in saliva components in patients with Alzheimer's disease (AD) of different severity and determine if any of these components could be a biomarker of this disease. Therefore, a panel of selected analytes related to the amyloid cascade, the immune and adrenergic systems, among others, were analyzed in the saliva of patients with Alzheimer's disease.

Methods: A total of 152 patients with AD and controls were included. The severity of the disease was established according to the Global Deterioration Scale. Unstimulated whole saliva was collected.

Results: Salivary amyloid-β42 was significantly lower, and complement C4 was significantly higher in the patients with AD than in the controls (p < 0.05 in both cases). Only complement C4 maintained its significant effect in the multivariate regression analysis. However, the area under the receiver operating characteristic curve of C4 was 0.613. No changes were found in any analyte regarding the severity of the disease.

Conclusions: A decrease in amyloid-β42 and an increase in complement C4 were detected in the saliva of patients with AD, but the changes did not show a high diagnostic performance for the detection of AD and were not associated with its severity.

Clinical relevance: Although some analytes showed significant differences in saliva in patients with AD, in our study conditions the salivary biomarkers analyzed were not of enough diagnostic utility for being used in routine.

Keywords: Amyloid-β; Complement; Dementia; Saliva; Tau.