Exploring the methods of salivary analysis in the diagnosis of Alzheimer's disease: A scoping review

Alzheimer's disease is a common type of dementia. It is a progressive neurodegenerative disease that starts with mild memory loss and may progress to loss of ability to convey a conversation and respond to the surrounding. Early detection can help in the management of this disease. In this review, we attempted to find the most accurate method for salivary biomarkers detection, which can aid in the early diagnosis of Alzheimer's disease. For this scoping review; PubMed, Scopus, and Google Scholar online databases were searched to find studies and articles that test the salivary biomarkers for the diagnosis of Alzheimer's disease. Eleven studies were eligible for our research. Ten were case–control, and one was a cohort study. Seven of the studies used the enzyme-linked immunosorbent assay (ELISA) method, five of which showed diagnostic potential. Two studies used Luminex assay and photomultiplier tube, showing similar results to ELISA. AbsoluteIDQ®p150 Kit and faster ultra-performance liquid chromatography-mass spectrometry analysis and pattern recognition techniques tested different metabolites with potential diagnostic significance. Furthermore, another study using an extended gate ion sensitive field effect transistor sensor related salivary trehalose sugar to Alzheimer's disease. Different reliable biomarkers were detected using ELISA kit and appear to be effective in disease detection. Further studies and clinical trials on a large scale are required to determine the most accurate method of detecting Alzheimer's disease.