SNCA and Parkinson disease: Two years later, saliva samples from 201 PD sufferers and 67 healthy volunteers were analyzed by means of Luminex assay (Bio-Rad, Abcam) for total and oligomeric α-synuclein, as well as the relationship between α-synuclein and α-synuclein SNP (single-nucleotide polymorphism) variants [33].