Blood test could improve the accuracy of Parkinson’s diagnosis and monitoring

A new blood test for a toxic protein may help detect Parkinson’s long before symptoms show.

Researchers at the University of Oxford have developed a blood test which could allow Parkinson’s to be diagnosed earlier and more accurately, years before people experience physical symptoms.

In Parkinson’s, a protein called alpha-synuclein starts to stick together and accumulate in the brain. The clumps of protein can cause damage to the surrounding cells. It’s thought this happens many years before the most recognisable symptoms of Parkinson’s start to show, such as a slowness of movement and tremor.

This new research shows how a blood test that can detect changes in alpha-synuclein could be used to identify people in the early stages of Parkinson’s.

Why use a blood test?

When alpha-synuclein starts to clump together in the cell, the cell tries to rescue itself by issuing a stress signal. The cell starts to package up bits of the toxic alpha-synuclein protein into small bubbles, called vesicles, and expel them from the cell. The vesicles then make their way into the bloodstream. The blood test designed by the researchers in Oxford looks for these vesicles of alpha-synuclein.

Toxic alpha-synuclein can also be found in the cerebrospinal fluid (CSF), which surrounds the brain and the spinal cord. Earlier this year, researchers announced a new test could diagnose Parkinson’s by looking for alpha-synuclein in the CSF via an injection into the spine, called a lumbar puncture. Read more about the new lab test.

However, a lumbar puncture is not suitable for everyone, and can come with some risks. If it’s possible to see similar results using a blood test, this might make a test more accessible for everyone with Parkinson’s.

What did the researchers find?

576 people with varying risks of developing Parkinson’s took part in this study, ranging from those with a high risk of developing Parkinson’s, to a low risk group. The researchers also studied blood samples from people who had already been diagnosed with Parkinson’s.

Using the test to look at the amount of alpha-synuclein in the blood, the researchers were able to correctly identify whether an individual had a high or low risk of developing Parkinson’s 9 out of 10 times. The researchers found that those with the highest risk of developing Parkinson’s had twice the amount of alpha-synuclein in their blood samples than those with a lower risk of developing the condition.

The blood test was also able to identify people who would go on to develop Parkinson’s and Parkinson’s dementia with an accuracy of 80%, up to 7 years before diagnosis. These people had much higher levels of alpha-synuclein in the blood, and comparatively lower levels of alpha-synuclein in the spinal cord. This suggests that the cells are trying to clear away the clumps of alpha-synuclein as they build up, to try and protect themselves from damage.

Read the published paper in full in JAMA Neurology.

Emma Rodgers, Research Communications Officer at Parkinson’s UK, comments:
"Currently, no definitive diagnostic test exists for Parkinson’s. But this is an extremely active area of Parkinson’s research. Research results in 2023 have shown a flurry of potential tests to help identify Parkinson's earlier.

"These tests still need refining, and it will be a while before they are able to be used in the diagnosis of Parkinson’s. But it’s exciting to see so much progress in this area. These tests could offer an objective way to measure whether new treatments being tested in clinical studies are working. Better tools could not only be used as a way to find new treatments, but also to identify people at risk before Parkinson’s symptoms show so we can stop the very early stages of the condition."