In total, 16 protein markers were selected, all of which are proposed to be associated with the major pathways of PD pathogenesis, such as protein aggregation (Aβ40, Aβ42, α-syn, p-Tau, t-Tau and NFL), inflammation (FLT3LG, MMP2, HMGB1, OPN and IL-6), oxidative stress (DJ-1 and S100β), lipid metabolism (ApoA1) and ubiquitin proteasome proteolysis (UCHL1) [13, 15, 21, 23–31, 33, 34, 37, 53, 54]. Here, MMP2 is linked to Parkinson disease.