Receiver operating characteristic (ROC) curves (Fig. 6b) revealed a high sensitivity (>75%) of the sFIDA assay in detecting α-synuclein aggregates in stool of iRBD patients versus healthy controls or PD patients but a lower specificity (iRBD vs. PD: 52.1%; iRBD vs. HC: 49.0%; Table 2). This evidence concerns the gene SNCA and Parkinson disease.