A “game-changing” new technique could pave the way for doctors to diagnose Parkinson’s disease long before symptoms appear.
Parkinson’s is caused by the build-up of abnormal proteins known as alpha-synuclein (alphaSyn) throughout the brain and the nervous system, which is thought to occur years before physical symptoms such as tremors and muscle stiffness begin to emerge.
However, symptoms vary from person to person and are shared by a number of other illnesses, further complicating diagnosis attempts.
Nearly 150,000 people in the UK are estimated to live with Parkinson’s and there is currently no specific test for the condition, making it difficult to diagnose.
But new research, published in The Lancet Neurology journal, appears to confirm that a method known as alpha-synuclein seed amplification assay (alphaSyn-SAA) can accurately identify the build-up of these proteins – and potentially therefore which people are at risk of developing the condition.
Scientists not involved in the study said the findings lay “the foundation for a biological diagnosis of Parkinson’s”, describing the technique as a “game-changer” in Parkinson’s diagnostics, research, and treatment trials.
“Identifying an effective biomarker for Parkinson’s disease pathology could have profound implications for the way we treat the condition, potentially making it possible to diagnose people earlier, identify the best treatments for different subsets of patients and speed up clinical trials,” said co-lead author Professor Andrew Siderowf, of the University of Pennsylvania.
The study involved 1,123 participants, making it one of the largest so far to assess the usefulness of the alphaSyn-SAA technique – which amplifies miniscule amounts of the abnormal proteins to the point that they can be observed using standard laboratory techniques.
It included people with a Parkinson’s diagnosis, at-risk individuals with gene variants – GBA and LRRK2 – linked to the condition, and prodromal people – those showing early non-motor symptoms such as sleep disturbance or loss of smell.
Researchers took samples of a fluid surrounding the brain and spinal cord from each participant and analysed it using the technique.
In prodromal participants, they found that 89 per cent of those experiencing loss of smell had positive alphaSyn-SAA results, falling slightly to 85 per cent in those with REM sleep behaviour disorder – a known precursor to Parkinson’s.
The results were more varied among people with genetic forms of Parkinson’s, with 96 per cent of those with the GBA variant showing positive results, compared with 68 per cent of those with LRRK2.
The symptom found to most strongly predict a positive result was loss of smell, which is common in prodromal people and those with a Parkinson’s diagnosis.
“While loss of smell appears to be a strong predictor of Parkinson’s disease, it’s important to note that this study identified individuals with positive alphaSyn-SAA results, but who had not yet lost their sense of smell,” said author Dr Tanya Simuni, of Northwestern University.
This indicates that alpha-synuclein pathology may be present even before there is a measurable loss of sense of smell, Dr Simuni said, adding that further research is needed to find out how patients’ sense of smell may change over time and how this relates to the protein’s build-up.
The scientists warned that longer-term studies with even larger sample sizes are still needed.
However, two scientists not involved in the study – professors Daniela Berg and Christine Klein, of Germany’s University Hospital Schleswig-Holstein – hailed the findings as laying “the foundation for a biological diagnosis” of Parkinson’s.
While the technique is a “game-changer”, they said it would need to be made available in the form of blood tests in order to harness its full potential.
