Use of Saliva for Alzheimer's Disease Diagnosis

Overview

Although saliva is not generally regarded as one of the most interesting biological fluids, the fact that it can be sampled using simple, noninvasive methods makes it an interesting alternative to cerebrospinal fluid (CSF) or blood for diagnostic purposes. The use of salivary diagnostics is moreover increasing these past 10 years, as shown with the abundant literature as well as various clinical trials. Saliva collection which is now well standardized has the major advantage of being simple and non-invasive. An original study had already discussed possible changes in the salivary composition in Alzheimer's disease (AD). The feasibility and the potential interest of measuring saliva concentration of the amyloid peptides was reported in an article published recently. The prospect of using saliva for early diagnosis and monitoring of AD is thus of major interest and the objective of the current trial.

Saliva samples To minimize the circadian effects, saliva specimens were all collected between 9:00 and 11:00 a.m. Prior to the sampling procedure, participants rinsed out their mouths three times with water. To induce salivary production, patients were asked to chew neutral or citric acid impregnated Salivette cotton swabs for exactly 60 seconds. Saliva specimens were centrifuged for 2 minutes at a rate of 1000 g to yield clear saliva, which was aliquoted into 500 µL samples in LoBind tubes and stored at -80°C before being analyzed. Design of the study Saliva sampling will be performed at V0 (M0), V1 (M12) and V2 (M24). Blood sampling will take place also in V1 (M12). The cases and the controls will be systematically reviewed 12 months after inclusion with a new saliva collection and a cognitive assessment (for cases and controls). Amyloid peptide quantification Levels of human endogenous Aβ40 and Aβ42 in saliva and human plasma samples are determined with human specific enzyme-linked immunosorbent assay (ELISA) (Biosource International, Invitrogen), according to the manufacturer's instructions. Briefly, 50 μl of saliva and plasma samples were added in triplicate to the microtiter wells. Detection limit of the assay was 6 pg/ml for Aβ40 and 1 pg/ml for Aβ42.