Measurement of serum cystatin C: A valuable tool for evaluating dyskinesia in Parkinson's disease.

Although cystatin C (Cys C) has been implicated in the pathophysiology of Parkinson's disease (PD), whether it can be used as a tool for evaluating dyskinesia is unknown. In the present study, the association of Cys C with dyskinesia in PD patients was investigated. Fasting serum Cys C levels were measured from 120 PD patients and 156 healthy controls. Demographic information was collected for all patients. In addition, levodopa (L-dopa)-equivalent dose, Unified Parkinson's Disease Rating Scale (UPDRS) score, Hoehn and Yahr (H&Y) stage, and dyskinesia were assessed in PD patients. Receiver operating characteristic (ROC) curves were adopted to assess the evaluating accuracy of Cys C levels for distinguishing dyskinesia in PD patients. Patients with PD exhibited significantly higher serum Cys C levels compared with heathy controls. Dyskinesia was observed in 32 patients (26.7%). Multiple logistic regression showed serum Cys C levels (odds ratio, OR 12.93; 95% confidence interval, CI 1.08-54.23; p = 0.043), duration of disease (OR 1.03, 95% CI 1.01-1.05, p = 0.001) and UPDRS II score (OR 1.07, 95% CI 1.01-1.14, p = 0.019) were independently associated with dyskinesia. The ROC curve for the Cys C levels yielded a valuable accuracy for distinguishing dyskinesia in PD patients. Serum Cys C levels were independently associated with dyskinesia and may be a valuable screening tool for differentiating dyskinesia in PD patients. Although the pathophysiological mechanism of PD is complicated, the results from our study provide a better understanding of the association between Cys C and dyskinesia in PD patients and may yield insights into the pathogenesis of PD.