A Systematic Review on the Feasibility of Salivary Biomarkers for Alzheimer’s Disease

Background: Early AD diagnosis is critical for ameliorating prognosis and treatment. The analysis of CSF biomarkers yields accurate results, but it necessitates a lumbar puncture procedure. Screening for peripheral biomarkers in saliva is advantageous since this medium is noninvasive and inexpensive to obtain. The objective of this systematic review is to analyze saliva biomarker studies which aim to diagnose AD. Methods: Titles, abstracts, and reference lists for publications from February 2004 to March 2019 were screened for by searching Google Scholar and PubMed. The inclusion criteria involved published studies that consisted of both AD and control groups. Results: 77 studies were screened, and 13 publications fulfilled the inclusion criteria. These selected publications were scrutinized and included in this review. Numerous biomarkers were analyzed, including Aβ42, tau, and various salivary metabolites. Conclusion: Aβ42, tau, lactoferrin, and various metabolites might serve as a reliable biomarkers for AD diagnosis. However, these studies must be replicated with a large sample size. It is also important to standardize the analytical methods of measuring salivary biomarkers to establish coherence for the selection of valid AD biomarkers. Saliva composition can be affected by production rate, circadian rhythms, and oral health, so their cumulative effect on the accuracy of saliva testing requires further investigation. Keywords: Alzheimer, biomarker, saliva