Research has shown that several serum oxidant factors may act as important biomarkers to predict the disease severity in neurodegenerative diseases, such as Parkinson’s disease (PD) (Hu et al., 2016; Sampat et al., 2016) and amyotrophic lateral sclerosis (ALS) (Tetsuka et al., 2013; Paganoni et al., 2018; van Eijk et al., 2018), including uric acid (UA), serum creatinine (Scr), and cystatin C (Cys-C). Here, CST3 is linked to Parkinson disease.