Parkinson's disease (PD) affects approximately 4 million people globally and is most commonly seen in people over the age of 50. The disease is a progressive disorder of the nervous system, and presents a number of movement and cognitive symptoms, thereby greatly affecting a patients quality of life. The use of scales for assessment in neurological disorders such as PD arises from the need to quantify disorders and states (such constructs as disability, symptoms, quality of life). Assessment scales are often categorised into two categories: generic (ie. those scales usable in any health condition), and specific (ie. scales developed for exclusive use in PD). They can have a variety of components: single-item and multi-item or composite scale; unidimensional and multidimensional; and as disease-centered and patient-centered measures. The creation and validation of scales is complex, with scales undergoing numerous studies to assess criteria such as acceptability, reliability, and responsiveness. In the process of validation of a scale the following attributes should be tested to ascertain whether a scale is an effective instrument of measurement. This Guide assesses the key clinimetric attributes in the assessment of PD, with the  intention to offer rapid and pragmatic information on the most relevant scales used in PD.

Dr Pablo Martínez-Martín, Ph.D is a graduate in Medicine, and Neurology, and a Tenured Scientist for the Spanish Public Boards of Research. Since 2006, he has served as the Scientific Director of the Research Unit for Alzheimer's Disease, CIEN Foundation, the Alzheimer Centre Reina Sofía Foundation, and a Member of the Consortium for Biomedical Research in Neurodegenerative Diseases (CIBERNED), Carlos III Institute of Health (Spanish Ministry of Economy and Competitiveness). Dr Martinez-Martin's research interests are: clinical assessment and rating scales; patient-reported outcomes, particularly health-related quality of life; neurodegenerative diseases; Parkinson's disease; and Alzheimer's disease and dementia. He has received 14 awards for scientific activities in Neurosciences and aging. Dr. Martínez-Martín has authored over 290 articles in peer-reviewed scientific journals and 87 book chapters, and is editor or co-editor of 17 books and monographs. He has participated with 348 platform or poster reports and 168 talks in scientific forums (congresses, symposia, expert workshops) and has given 159 lectures as invited professor in teaching institutions. At present, he is an active member of several study groups with the Spanish Society of Neurology and the Movement Disorder Society, as well as international steering committees for research and collaborative groups.