"There is currently no diagnostic test for Parkinson's disease," said study author Charles Adler, with the Mayo Clinic Arizona and a Fellow of the American Academy of Neurology.
"We have previously shown in autopsies of Parkinson's patients that the abnormal proteins associated with Parkinson's are consistently found in the submandibular salivary glands, under the lower jaw, and this is the first study demonstrating the value of testing a portion of the saliva gland to diagnose a living person for Parkinson's disease," Adler said in a statement.
"Making a diagnosis in living patients is a big step forward in our effort to understand and better treat patients," Adler added.
The study involved 15 people with an average age of 68 who had Parkinson's disease for an average of 12 years, and responded to Parkinson's medication and did not have known salivary gland disorders.
Biopsies were taken of two different salivary glands: the gland under the lower jaw and the minor salivary glands in the lower lip. The biopsied tissues were stained and reviewed for evidence of the abnormal Parkinson's protein.
In four of the initial lower jaw biopsies, while researchers were still perfecting the technique, not enough tissue was available to complete the tests.
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The abnormal Parkinson's protein was detected in nine of the 11, or 82 per cent, of the patients with enough tissue to study.
"While still under analysis, the rate of positive findings in the biopsies of the lower lip glands appears to be much lower than for the lower jaw gland," Adler said.
"This study provides the first direct evidence for the use of lower jaw gland biopsies as a diagnostic test for living patients with Parkinson's disease," he said.
"This finding may be of great use when needing tissue proof of Parkinson's disease, especially when considering performing invasive procedures such as deep brain stimulation surgery or gene therapy," Adler said.
The study will be presented at the American Academy of Neurology's 65th Annual Meeting in San Diego.