Parkinson's disease is the second most common neurodegenerative disease after Alzheimer's disease. It is a degenerative disorder of the central nervous system that often affects motor skills and is associated with progressive neuronal loss of the substantia nigra and other brain structures. It is a disease characterized by muscle rigidity, tremors and sometimes complete loss of movement.

The natural history of this disease varies from patient to patient with some progressing slowly over several years while others quickly become totally disabled. Correct diagnosis is crucial in the management of Parkinson's disease but there is currently no test available to aid in its diagnosis. The diagnosis is based on the presence of typical symptoms, which in the early stage of the disease may be difficult to define. Symptoms observed in Parkinson's can also be confounded by side-effects from some drugs used to treat other conditions. When symptoms progress to more severe stages they often become clearer and make diagnosis easier for the clinician.

Unlike Alzheimer's the clinical phenotype is rather homogenous and thus clinical diagnosis can be as high as 98.5% with experienced clinicians. However, studies on community based diagnosis of probable Parkinson's disease indicate the diagnostic accuracy can be as low as 53%. Moreover, population based studies indicate that at least 15% of patients with a diagnosis of Parkinson's disease do not fulfill the strict clinical criteria.

Early disease detection is also critical for development of new drugs. Existing Parkinson's drugs are all symptomatic reducing symptoms caused by declining production of dopamine. To develop drugs that reduce and even stop progression of the disease, diagnostic tools to identify the disease at an earlier stage are essential.

The potential for developing a blood-based gene expression test for Parkinson's disease was first shown by Scherzer et al [1]. With initial funding by the Michael J Fox Foundation and collaboration with experts at Harvard, DiaGenic is now with a grant from the Norwegian Research Council developing a blood-based gene expression test for the early diagnosis of Parkinson's disease.

1. Scherzer CR, Eklund AC, Morse LJ, Liao Z, Locascio JJ, et al. (2007) Molecular markers of early Parkinson's disease based on gene expression in blood. Proc Natl Acad Sci U S A 104: 955-960.