A pilot study with 16 PD patients, stratified via the stage of PD progression according to the Hoehn and Yahr (HY) stages (HY stages II and III), observed a significant decrease of complement proteins clusterin and C1r, as well as apolipoprotein A1 (ApoA1) in plasma EVs from PD patients versus HC (141). Here, APOA1 is linked to Parkinson disease.