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J Neural Transm (Vienna). 2019 Aug 10. doi: 10.1007/s00702-019-02062-4. [Epub ahead of print]

Salivary alpha-synuclein as a biomarker for Parkinson's disease: a systematic review.

Author information

1
1st Department of Neurology, School of Medicine, Eginition Hospital, National and Kapodistrian University of Athens, Vassilisis Sophias Avenue 72-74, 11528, Athens, Greece. annita139@yahoo.gr.
2
1st Department of Neurology, School of Medicine, Eginition Hospital, National and Kapodistrian University of Athens, Vassilisis Sophias Avenue 72-74, 11528, Athens, Greece.

Abstract

The search for a reliable, early-disease biomarker for Parkinson's disease (PD) that reflects underlying pathology is a high priority in PD research. Salivary alpha-synuclein (α-Syn) is an easily accessible biomarker for PD with promising results. Our aim was to evaluate the performance of salivary α-Syn as a diagnostic biomarker of PD. We identified 476 studies through a systematic literature review according to PRISMA guidelines. Finally, eight studies reporting data on salivary α-Syn were included in the review (1240 participants). The quality of studies was assessed by Newcastle-Ottawa scale. (1) Three studies showed that the total α-Syn levels were significantly lower in PD patients compared to healthy controls, while in another five there was no significant association. (2) In some studies, total salivary α-Syn was associated with demographic and clinical features; however, no consistent pattern emerged. In one study, total α-Syn levels were associated with poor cognitive performance in PD patients. (3) Four studies showed a higher salivary oligomeric α-Syn and oligomeric α-Syn/total α-Syn ratio in PD compared to healthy controls, while in another four there was no association. (4) One study concluded that genetic polymorphisms may influence total salivary α-Syn in PD patients. Taken together, the potential of salivary total α-Syn as a PD biomarker is still uncertain, whereas salivary oligomeric α-Syn appears quite promising. Pre-analytical and analytical factors of included studies were important limitations to justify the introduction of salivary α-Syn into clinical practice.

KEYWORDS:

Analytical factors; Oligomeric; Parkinson’s disease (PD); Salivary biomarkers; α-Synuclein (α-Syn)

PMID:
31401695
DOI:
10.1007/s00702-019-02062-4

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