Salivary alpha-synuclein in the diagnosis of Parkinson's disease and Progressive Supranuclear Palsy

Introduction: Alpha-synuclein (α-syn) aggregation is the pathological hallmark of Parkinson's Disease (PD). In this study, we measured α-syn total (α-syn_total), oligomeric α-syn (α-syn_olig) and α-syn_olig/α-syn_total ratio in the saliva of patients affected by PD and in age and sex-matched healthy subjects. We also compared salivary α-syn_total measured in PD with those detected in Progressive Supranuclear Palsy (PSP), in order to assess whether salivary α-syn can be used as a biomarker for PD and for the differential diagnosis between PD and PSP.

Methods: We studied 100 PD patients, 20 patients affected by PSP and 80 age- and sex-matched healthy subjects. ELISA analysis was performed using two commercial ELISA platforms and a specific ELISA assay for α-syn aggregates.

Results: We detected lower α-syn_total and higher α-syn_olig in PD than in healthy subjects. Conversely in PSP salivary α-syn_total concentration was comparable to that measured in healthy subjects. Receiver Operating Characteristic analyses revealed specific cut-off values able to differentiate PD patients from healthy subjects and PSP patients with high sensitivity and specificity. However, there was no significant correlation between clinical and molecular data.

Conclusion: Salivary α-syn detection could be a promising and easily accessible biomarker for PD and for the differential diagnosis between PD and PSP.