What's Hot in PD? Are Blood Tests for Parkinson’s Disease on the Horizon?

Patients and family members have been waiting for news about the possibility of a blood test to detect Parkinson’s disease. In November, a small article was published in the FASEB journal where Foulds and colleagues reported the results of a pilot study that examined phosphorylated alpha-synuclein as a potential candidate for use as a blood test in detection of Parkinson’s disease. In this month’s What’s Hot column we will examine this recent paper, discuss the current state of the field, and discuss how the development of a blood test could affect those at risk, and those suffering from Parkinson’s disease.

The investigation focused on a protein called alpha-synuclein which is thought to be important to the cause of Parkinson’s disease, and is a critical component in the deposits that accumulate in the Parkinson brain. The authors measured alpha-synulcein in both Parkinson’s disease and in control patients. They reported that Parkinson’s disease patients had an abnormal phosphorylated form of alpha-synuclein. The changes in the blood were sampled over a three-month period, and were found to be stable in 30 patients; and they were in general, not present in control subjects.

There were, however, several issues with this study. First, the sample size was too small to conclude that this test will prove viable in a much larger population of Parkinson’s disease patients. Second, the authors provided little information on the actual patients they studied. Parkinson’s disease is not one disease, and as groups develop blood tests, they will need to carefully characterize and report the clinical symptoms of the patients studied. Additionally, groups will need to be cautious in understanding which types of patients will reveal blood changes, and more importantly, which groups will not. Finally, changes in phosphorylated alpha-synuclein could possibly occur in other Parkinsonian syndromes, other neurological diseases, and other systemic diseases. These other diseases must be carefully investigated. Though there were important methodological issues with this study, it is still likely we will see Parkinson’s disease blood tests and biomarkers in the near future.

If successfully developed how would a blood test for Parkinson’s disease be used? There are several potential options for this emerging technology. First, if a disease modifying therapy can be developed, then identifying at risk patients for early intervention could be critical. A blood test could potentially identify those at risk, and help to facilitate early intervention. Another important use for a blood test could be in monitoring the symptomatic treatment of current Parkinson’s disease sufferers, especially in those enrolled in drug trials. The test would however, need to reflect changes in biological activity over time, and would also need to closely correlate to changes in disease state (e.g. progression of symptoms). 

A blood test for Parkinson’s disease would also introduce important ethical considerations, especially for asymptomatic individuals. Though the test may not reflect genetic status, it may unmask a Parkinson’s disease diagnosis. Revealing a potential risk to develop Parkinson’s disease could profoundly change a person’s life. Studies of genetic counseling have revealed that once patients understand the implications of a blood/genetic test, they will often decline it. Additionally, for currently symptomatic individuals, close monitoring of disease status could result in stress, anxiety, and worry that may translate into a worsened overall quality of life.

It is important to understand that many groups around the world are attempting to develop blood tests and biomarkers for Parkinson’s disease. It is likely that many of the methodological limitations limiting blood tests will soon wane, and that successful approaches will emerge. As we move forward it will be important for the field to clearly define the potential uses of a blood test, and especially to protect patients and also to protect families. It is also important that patients understand that there will likely be more than one blood test in the future, and that close communication with their doctors will be critical in deciding which test, or which battery of tests would be appropriate to check. In summary, the development of blood tests and biomarkers has the potential to improve the lives of many Parkinson’s disease patients, and also to push the research horizon in a positive direction. These tests must be pursued cautiously and with an open mind as to how they will affect both the population at risk, and the people currently living with Parkinson’s disease.

Selected Reference

Foulds, P. G., Mitchell, J. D., Parker, A., Turner, R., Green, G., Diggle, P., Hasegawa, M., Taylor, M., Mann, D., Allsop, D. Phosphorylated alpha-synuclein can be detected in blood plasma and is potentially a useful biomarker for Parkinson’s disease. FASEB J. 25, 4127–4137 (2011).www.fasebj.org

You can find out more about our National Medical Director, Dr. Michael S. Okun, by also visiting the Center of Excellence, University of Florida Health Center for Movement Disorders and Neurorestoration. Dr. Okun is also the author of the Amazon #1 Parkinson's Best Seller 10 Secrets to a Happier Life and 10 Breakthrough Therapies for Parkinson's Disease.

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