Plasma Alpha Synuclein as a Potent Biomarker of Diseases with Synucleinopathies

Objective: We explored whether plasma α-syn be used as a potential biomarker for synucleinopathies. Materials and Methods: α-syn levels in plasma from 54 Parkinson’s disease dementia (PDD) and dementia with Lewy bodies (DLB) patents, 31 Alzheimer’s disease dementia (AD), and 29 controls were measured by enzymelinked immunosorbent assay (ELISA). Results: The mean age of the synucleinopathies group, the AD group, and the normal controls was 72.70, 74.26, and 62 years old. The median plasma α-syn levels in the synucleinopathies group, AD group and controls were 9.72 (4.41-25.30), 16.78 (7.68-51.41) and 16.65 (10.37-32.72) ng/ml, respectively (Independent-Samples Kruskal-Wallis test, p = 0.026). The α-syn levels in the synucleinopathies group were lower than those of AD and controls. There was a fair correlation between plasma α-syn levels and the sum of the Unified Parkinson’s Disease Rating Scale (UPDRS) part 3 (spearman correlation coefficient r = -0.261, p = 0.021) but not with cognition measured by Thai Mental Status Examination (TMSE). The area under the receiver operating characteristic curve (ROC) was 0.710 between the PDD and DLB vs non synucleinopathies group (AD and normal controls) (SE = 0.052, p ≤ 0.001). At the cut-off levels of 11.4 ng/ml indicated a sensitivity of 58% (95% CI 43.21-71.81%), specificity of 84.78% (95% CI 71.13-93.66%), positive predictive value (PPV) of 80.56%, a negative predictive value (NPV) of 65% and a precision of 70.83%. Conclusion: The present results suggest that plasma α-syn could be a potential biomarker to differentiate synucleinopathies from Alzheimer’s disease and the elderly with normal cognition.