Biomarkers in Parkinson's Disease.

Parkinson's disease (PD) is a leading cause of disability worldwide, and there is a pressing need to develop therapeutics to slow or halt disease progression. The identification of reliable biomarkers of PD at all stages of disease will be a critical step toward optimizing diagnosis and therapeutic development. For PD, biomarkers could serve multiple important functions. There have been significant advances in biomarker development in PD in recent years, and in this review, the authors summarize the current state of the PD biomarker field covering major advances in fluid, tissue, and neuroimaging biomarkers.