SPP1 and Parkinson disease: Among the 700 plasma analytes, 68 were specific to AD (NEFL, MSMB), 62 to PD (CBFB, STX12), four to FTD (HS3ST5, SNRPD3, BDP1, ACTN2), and two to DLB (PRXL2A, IL17F), with just 26 (ALDH1A1, SPP1) commonly expressed among all four NDs (Fig 2D&F, Supplementary Fig. 4).