Early diagnosis of the disease can be challenging because there are no biomarkers, neuroimaging or other clinical tests available to confirm the diagnosis. Parkinson's disease (PD) diagnosis is currently based on the presence or absence of various clinical features and the experience of the treating physician.
The signs and symptoms present in early PD correspond to a number of other movement disorders, particularly other forms of Parkinsonism, such as multiple system atrophy, drug-induced Parkinsonism, and vascular Parkinsonism, as well as diffuse Lewy body disease and essential tremor. Nevertheless, diagnosis of PD based on clinical features and response to antiparkinsonian medication can be achieved with a fairly high level of accuracy, particularly when made by a physician specialising in movement disorders.1
1 Pahwa, R; Lyons, K. Early diagnosis of Parkinson's disease: recommendations from diagnostic clinical guidelines. Am J Manag Care; 2010