Researchers at the Weill Cornell Medical College in New York City have come up with a blood test that profiles molecular biomarkers, giving hope that it could become the first accurate diagnostic test for Parkinson's disease.
The new test is based on alterations in dozens of small molecules in serum, known as "metabolomic" alterations, which form a unique pattern in people with Parkinson's disease.
The study was led by Dr. M. Flint Beal, chairman and Anne Parrish Titzell Professor of Neurology at Weill Cornell Medical College, and neurologist-in-chief at NewYork-Presbyterian Hospital/Weill Cornell Medical Center.
"A reliable blood test for Parkinson's disease would revolutionize not only the care of people with this debilitating illness, it would facilitate research as well. Right now, a Parkinson's diagnosis is made solely on a clinical review of symptoms we have no biologic test. At best, a symptom-based screen is still only 90 percent accurate," he said.
He added: "That can cause real problems, because that remaining 10 percent of patients who may have look-alike conditions such as multi-system atrophy or progressive supranuclear palsy end up getting treated with Parkinson's drugs. These medicines may appear to help them a little while, but in the meantime, they haven't been getting the treatment that's necessarily best for them."
He also noted that an early-detection test can turn out to be extremely beneficial in tracking the health of patients appearing to be at higher risk for Parkinson's, such as those with a family history of the disease. He said that due to the absence of an accurate screen, the integrity of clinical trials is at stake.
"Every time you do a clinical trial into Parkinson's and you have patients that are misdiagnosed, it enters 'noise' into the analysis, skewing the results. A truly reliable test could help eliminate that," noted the researcher.
Thus, encouraging results for the new test, based on a patient's "metabolomic profile," are so important.
Metabolomics is the study of changes in thousands of distinct, very small molecules found in body fluids or tissues.
"Anytime you have a genetic or environmental perturbation, these molecules are altered in specific ways," explained Beal.
As Parkinson's treatment could trigger some of these alterations on its own, this led the researchers to first compare metabolomic patterns in the blood of Parkinson's patients who were not undergoing treatment as against those who were medicated.
"That gave us a 'medication-free' profile that we could use going forward," explained Beal.
Later, blood samples from 66 patients with Parkinson's disease were measured against 25 healthy controls (most of whom were the patients' spouses). The metabolomic analysis included over 2,000 small molecules found in the blood.
"We discovered a clear differentiation between the metabolomic profiles of the Parkinson's disease patients versus those of the controls.. No one molecule was definitive, but a pattern of about 160 compounds emerged that was highly specific to Parkinson's patients," said Beal.
The significance of many individual compounds to the disease remains unknown and this will be the focus of future study. However, changes in a few well-known metabolites linked to oxidative stress were clearly linked to Parkinson's. These included low levels of the antioxidant uric acid; an increase in blood levels of another antioxidant, glutathione; and increased levels of a marker for oxidative damage called 8-OHdG.
"Together, these and other compounds were arranged into a metabolomic pattern that identified Parkinson's disease with great accuracy," said Beal.
The findings of the study are published in the journal Brain.