Biomarkers in Parkinson's disease: an update

This review article is focused upon the most recent biomarker studies of Parkinson's disease. It provides an update on promising areas of biomarker research in a rapidly expanding field, and discusses future directions that might lead to successful development of Parkinson's disease biomarkers. Studies of molecular-genetic and biochemical biomarkers of Parkinson's disease have not only targeted hypothesis-driven measures of specific substrates involved in processes such as protein misprocessing, but also have made use of sophisticated analyses such as transcriptomic, proteomic, and metabolomic approaches. Whereas none of these are yet established as Parkinson's disease biomarkers, brain imaging using the 123I-ioflupane ligand with single-photon emission computed tomography was recently approved in the United States to aid in Parkinson's disease diagnosis, and research on other imaging modalities is ongoing. Neurophysiological tests are also being adapted for biomarker research, and we review recent promising data. The search for effective biomarkers for diagnosis and surveillance of Parkinson's disease continues. A battery of biomarkers comprising different modalities might be required to address clinical needs in this complex disorder. Critically, collaborative efforts including centralized tissue repository and clinical research infrastructure that are being organized will advance this field further.