α‐Synuclein in blood cells differentiates Parkinson’s disease from healthy controls

OBJECTIVE: To determine whether blood cells expressed α‐Syn can differentiate Parkinson’s disease (PD) from healthy controls (HC). METHODS: The concentrations of α‐Syn were determined in samples of blood cell pellets using a quantitative Lipid‐ELISA assay. In addition, the levels of total protein, hemoglobin, iron and H‐ferritin were determined. The study includes samples from the Biofind cohort (n = 46 PD and 45 HC) and results were validated with an additional cohort (n = 35 PD and 28 HC). RESULTS: A composite biomarker consisting of the concentrations of total α‐Syn, proteinase‐K resistant (PK(res)) α‐Syn and phospho‐Serine 129 α‐Syn (PSer 129), is designed based on the analysis of the discovery BioFIND cohort. This composite biomarker differentiates a PD subgroup, presenting motor symptoms without dementia from a HC group, with a convincing accuracy, represented by an AUC = 0.81 (95% CI, 0.71 to 0.92). Closely similar results were obtained for the validation cohort, that is, AUC = 0.81, (95% CI, 0.70 to 0.94). INTERPRETATION: Our results demonstrate the potential usefulness of blood cells expressed α‐Syn as a biomarker for PD.