The study, which enrolled 15-patient, collected biopsies from two different saliva glands including the submandibular gland and the minor saliva glands in the lower lip.

The study showed that the abnormal protein associated with Parkinson’s was detected in nine of the 11 patients, who had enough tissue to study.

In addition, the rate of positive findings in the biopsies of the lower lip glands appeared much lower than for the lower jaw gland.

Mayo Clinic neurologist and study author Charles Adler said the clinic has previously shown in autopsies of Parkinson’s patients that the abnormal proteins associated with Parkinson’s are consistently found in the submandibular saliva glands, found under the lower jaw.

"This study provides the first direct evidence for the use of submandibular gland biopsies as a diagnostic test for living patients with Parkinson’s disease," Adler added.

"This finding may be of great use when needing definitive proof of Parkinson’s disease, especially when considering performing invasive procedures such as deep brain stimulation surgery or gene therapy."

The study, which was funded by the Michael J. Fox Foundation for Parkinson’s Research, will be presented at the American Academy of Neurology’s annual meeting which will be held in San Diego, US, in March 2013.