Calculating the ratio of oligomeric α-synuclein (o-α-syn)/total α-synuclein (t-α-syn) can distinguish PD from controls with a specificity of 90.6% and sensitivity of 89.3% with an area under the curve (AUC) of 0.948 (Tokuda et al., 2011). The gene discussed is SNCA; the disease is Parkinson disease.