Hopes are high that the blood test will open up possibilities of determining the risk of developing the disease even before tremors and other symptoms appear.
There is also the hope that the discovery will lead to the development of new drugs to treat the progressive degenerative disorder of the central nervous system.
The results of the research were published July 2 in the Annals of Neurology, the journal of the American Neurological Association.
About 150,000 people in Japan, mainly the elderly, have been diagnosed with Parkinson's disease, which is caused by a drop in dopamine, which functions as a neurotransmitter in the brain.
Patients suffer from shaking and experience difficulty walking.
As symptoms often do not appear for years, early detection was considered almost impossible.
Medicine that supplements dopamine in the body is one current treatment method.
The team including Nobutaka Hattori, a neurology professor at Juntendo University's Faculty of Medicine, compared blood samples of 49 healthy individuals and 186 with Parkinson's disease.
One result found was that levels of the polyamine spermine were considerably lower among those with the disease. The team also focused on another polyamine called diacetylspermine.
Patients were found to have higher concentrations of the substance in their blood than healthy individuals. The levels were higher for patients with more severe symptoms.
Doctors until now diagnosed individuals with Parkinson's disease based on symptoms such as tremors. But the new discovery could lead to a more accurate and simpler way of determining if an individual looks likely to develop the disease.
The test would also allow doctors to determine the extent to which the disease had progressed.
The research team will now focus on ways for patients to ingest the substance that produces spermine. The hope is to delay or improve symptoms related to Parkinson's disease.
"While Parkinson's disease affects the brain, we have learned that it also leads to changes in metabolites found in the blood," Hattori said.
Hideyuki Okano, a professor of physiology at Keio University who has conducted research on Parkinson's disease and spinal cord injuries, said, "The new marker may allow for diagnosing of Parkinson's disease before any symptoms related to motor functions appear."
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