Rates of Parkinson's disease are increasing, and as populations around the world start to age, it's expected that by 2040, the number of cases will have doubled. The disease is particularly difficult to diagnose, and most people with Parkinson's do not find out until it has already progressed for ten years or more. During that time, clumps of an abnormal protein called alpha-synuclein have begun to accumulate, which causes the death of important neurons. By the time of diagnosis, many neurons are already lost.
A new blood test could help identify those who are at risk for the disease, however. Clinicians may be able to help people limit neurodegeneration, or apply new therapeutics as soon as they become available. The work has been reported in JAMA Neurology.
In this study, researchers assessed samples from 365 people who are at risk of developing Parkinson's, along with 282 unaffected individuals and 71 people who had already been diagnosed with genetic or sporadic Parkinson's disease. The investigators identified a subtype of extracellular vesicles, tiny sacs released by cells that contain a variety of molecules, in people who are likely to develop Parkinson's. The scientists created an assay that uses antibodies to analyze extracellular vesicles released by nerve cells that are found in blood. Their alpha-synuclein content can be measured with this technique.
People who were at the highest risk of Parkinson's had alpha-synuclein levels in extracellular vesicles that were twice as high. The test was able to distinguish between people at high risk from healthy individuals or those with low risk. This blood test was able to identify 80 percent of people in the study who went on to develop Parkinsons, in some cases more than seven years before their diagnosis.
"A robust assay is crucial because neuronally-derived extracellular vesicles constitute less than 10 percent of all circulating vesicles, and about 99 percent of alpha-synuclein in blood is released from peripheral cells, mostly red blood cells," noted Professor George Tofaris.
Previous work by this lab has identifed a pathway that leads to the elimination of alpha-synuclein in neurons. It may also be related to the pathophysiology of Parkinson's disease.
Sources: University of Oxford, JAMA Neurology
