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

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Abstract

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. Titles, abstracts, and reference lists for publications from January 2004 to February 2020 were screened for by searching Google Scholar and PubMed. The inclusion criteria involved published studies that consisted of both AD and control groups. 88 studies were screened, and 20 publications fulfilled the inclusion criteria. These selected publications were scrutinized and included in this review. Aβ42, tau, certain metabolites, and oral microbiota might serve as reliable biomarkers for AD diagnosis. These results showcase the legitimate feasibility of proteomic, metabolomic, and microbiotic compounds in saliva for AD diagnostics in the near future. Supplemental studies must consider standardizing the analytical methods of measuring salivary biomarkers to establish coherence for the selection of valid AD biomarkers. Validation studies will require a large sample size of biomarker-diagnosed individuals for independent populations. This ensures accuracy and rigidity for receiver operating characteristic (ROC) curves that can be set for the most optimal salivary biomarkers in future clinical settings.

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All analyzed and generated data in this study, as well as supplemental information are included in this manuscript.

Abbreviations

Aβ:

Amyloid beta

Aβ40:

Amyloid beta-40 protein

Aβ42:

Amyloid beta-42 protein

AchE:

Acetylcholinesterase

AD:

Alzheimer’s Disease

aMCI:

Amnestic mild cognitive impairment

ANS:

Autonomic nervous system

APP:

Amyloid Precursor Protein

CSF:

Cerebrospinal fluid

EG-ISFET:

Extended gate ion-sensitive field-effect transistor

ELISA:

Enzyme-linked immunosorbent-type assay

FTD:

Frontotemporal Dementia

LC-MS:

Liquid chromatography-mass spectrometry

PD:

Parkinson’s Disease

P-tau:

Phosphorylated tau

ROC:

Receiver Operating Characteristic

SIMOA:

Single molecule array

T-tau:

Total tau

UPLC-MS:

Ultra performance liquid chromatography-mass spectrometry

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MB conducted the literature search, extracted the data, selected the studies for inclusion, analyzed the data, and wrote the manuscript.

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Correspondence to M. Bouftas.

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Bouftas, M. A Systematic Review on the Feasibility of Salivary Biomarkers for Alzheimer’s Disease. J Prev Alzheimers Dis 8, 84–91 (2021). https://doi.org/10.14283/jpad.2020.57

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