Different diagnostic criteria for Parkinson disease: what are the pitfalls?

As there are no definite diagnostic tests or reliable biomarkers for Parkinson disease (PD), its diagnosis still relies on the presence of a combination of cardinal motor features, along with the exclusion of other causes of Parkinsonism and the presence of some of supportive features. To date, several diagnostic criteria have been developed for different purposes through expert opinions or comprehensive review of the literature. However, none of them are without limitations. In this article, we review different diagnostic criteria for PD which have been published in the English medical literature, highlighting specific limitations and pitfalls. With considerable progress in the understanding of PD, particularly in a view of diverse clinical symptomatology and its evolution, it will be difficult to establish a single criterion that is capable of capturing all cases at different disease stages. Rather, we should aim to develop a set of criteria which include a consensus on clinical gold standard or reliable biomarkers at different levels of diagnostic certainty for different purposes. Despite a more refined set of criteria that may aid in the recognition of PD, the accuracy of its diagnosis still largely depends on the observational skills and clinical sensitivity of the treating physician.