An international team of researchers compared the levels of a protein called neurofilament light chain in samples from over 500 people who had taken part in research into parkinsonisms.
They discovered people with atypical parkinsonisms had higher levels of the protein that those with Parkinson's or healthy controls.
What are parkinsonisms?
'Parkinsonism' is an umbrella term that describes many conditions that share some of the symptoms of Parkinson's, such as tremor, rigidity and slowness of movement.
Parkinsonisms include progressive supranuclear palsy, corticobasal syndrome and multiple system atrophy - these conditions are called atypical parkinsonisms.
Although these conditions share similar symptoms they are caused by different things going wrong inside the brain and need different treatment approaches.
It can be difficult to tell the difference between Parkinson's and atypical parkinsonisms as there is no definitive diagnostic test. In some cases, the symptoms that allow doctors to make a specific diagnosis appear slowly, over a longer period of time, as the condition develops.
Positive steps towards a simple test
Claire Bale, Head of Research Communications at Parkinson's UK, comments:
"This test is very promising as it could reduce the delays and distress so many people experience in getting a definitive diagnosis of Parkinson's.
"Research suggests that around 1 in 10 people initially diagnosed with Parkinson's actually have another parkinsonism. This not only means they do not receive the right treatment and care, but also contributes to the failure of clinical trials of new medications.
"While this is a positive step towards a simple, fast test to determine whether someone has Parkinson's or a parkinsonism, more research in larger groups is still needed to determine the technique's accuracy."