A panel of twelve proteins (FABP6, ICAM5, PLA2G1B, TRAF3IP2, CHGB, MASP1, SPAG1, AMOTL2, CEACAM18, CNTN2, FAM13A, and TRIM26) effectively differentiated between PD and HC with a reported AUC of 0.77. This evidence concerns the gene SPAG1 and Parkinson disease.