Using a combined protocol of immunoprecipitation and electrochemiluminescence assays, it was established that an α-synuclein level in L1CAM-immunocaptured exosomes of above 14 pg/mL is a robust biomarker for the differential diagnosis of PD and atypical parkinsonisms (ROC AUC = 0.98) [49]. Here, L1CAM is linked to Parkinson disease.