1. Department of Neurology, Zhujiang Hospital of Southern Medical University, Guangzhou, Guangdong 510282, P. R. China
2. Guangzhou Kingmed Center for Clinical Laboratory Co., Ltd, Guangzhou, Guangdong 510005, P. R. China
3. Department of Neurology, National Neuroscience Institute, Singapore General Hospital, Singapore
4. Duke-NUS Medical School, Singapore
5. Parkinson Foundation International Centre of Excellence at King’s College Hospital, and Kings College, Denmark Hill, London, SE5 9RS UK