A Scottish woman named Joy Milne made headlines in 2015 for an unusual talent: her ability to sniff out people afflicted with Parkinson’s disease, a progressive neurodegenerative illness that is estimated to affect nearly a million people in the U.S. alone. Milne has been working with scientists from the U.K. to identify the molecules that give Parkinson’s its distinctive olfactory signature. The team has now identified a specific set of molecules that are responsible for the disease and has developed a skin-swab-based test to detect them.
Milne, a 72-year-old retired nurse from Perth, Scotland, has hereditary hyperosmia, a condition that endows people with a hypersensitivity to smell. She discovered that she could sense Parkinson’s with her nose after noticing her late husband, Les, was emitting a musky odor that she had not detected before. She eventually linked the change in smell to Parkinson’s disease when her husband was diagnosed with it many years later. Les passed away in 2015.
In 2012 Milne met Tilo Kunath, a neuroscientist at the University of Edinburgh in Scotland, at an event organized by the research and support charity Parkinson’s UK. Although initially skeptical, Kunath and his coworkers decided to test Milne’s claims. They gave her 12 T-shirts, six from people with Parkinson’s and six from healthy individuals. She correctly identified the disease in six of the cases. The T-shirt she gave from a healthy person was from someone who was diagnosed with Parkinson’s less than a year later.
Kunath and Perdita Barran, a chemist at the University of Manchester, in England, and her colleagues searched for molecules that cause the change in smell Milne can detect. Mass spectrometry was used to identify the types and amounts of molecules in a sample sebum, an oily substance that is found on the skin’s surface. They found changes in fatty molecules , also known as lipids in Parkinson’s patients.
In their latest study, published on September 7 in the American Chemical Society journal JACS Au, the researchers revealed the results of using a simple skin-swab-based test to detect the lipid signature that is indicative of Parkinson’s. By comparing sebum samples from 79 people with Parkinson’s and 71 people without the illness, the team zeroed in on a set of large lipids that could be detected in a matter of minutes using a special type of mass spectrometry in which substances are rapidly transferred from a swab to an analyzer using just a piece of paper.
“I think it’s a very promising set of biomarkers,” says Blaine Roberts, a biochemist at Emory University, who wasn’t involved in the work. He says that there are still many questions about the accuracy of this test. The September 7 study authors reported the chemical profile of Parkinson’s signature. However, they did not provide an assessment of its accuracy. According to Barran, based on not-yet-published data, their test appears to be able to determine whether an individual has Parkinson’s with more than 90 percent accuracy.
Tiago Outeiro, a neuroscientist at the University of Gottingen in Germany, who was not involved with the research, says the sebum-based swab test is novel and has clear advantages, such as the ease of sample collection. Outeiro wonders if people with Parkinson’s disease-like symptoms, such as multiple system atrophy or multiple system atrophy, have similar chemical markers.
The team is currently working with local hospitals in order to determine if the sebum-based test could also be performed in clinical labs. This is a crucial step towards determining if it can be used for diagnostic purposes. Barran believes that the test will be used to identify patients who have been referred by their general practitioners for possible Parkinson’s. This will allow them to receive a quicker diagnosis. Barran states that there are currently thousands of people who are waiting to see a UK neurologist. It will take approximately two years to clear this list. Patients could send in skin swabs for analysis in the hospital laboratory to identify those most in need. Barran’s research team reached out to people on the waiting lists to ask if they would be willing to participate in a trial to determine if such skin-swab testing could help speed up the triage process.
Barran and her colleagues are also collaborating with a group at Harvard University to determine whether sebum-based biomarkers are detectable in people who have constipation, a reduced sense of smell or other early signs of Parkinson’s but have not yet received a diagnosis.
Milne inspired other groups to look for biomarkers that are based on the disease’s olfactory signature. This year researchers in China published a paper describing an electronic nose–an artificial-intelligence-based sensor modeled after the olfactory system–that sniffs out molecules present in the sebum of patients with Parkinson’s disease. Other groups in China, the U.K. and elsewhere have also been training dogs to sniff out the disease.
Parkinson’s is not the only disease Milne has a keen ear for. She’s also reported noticing a unique smell in people with Alzheimer’s, cancer, and tuberculosis and is working with scientists to see whether a specific olfactory signature of those diseases can be deduced.
Milne hopes that this work will eventually benefit patients with these conditions. “My husband suffered from [Parkinson’s] for 21 years after his diagnosis, but he had it many years before that,” Milne told Scientific American in 2015. “I would like to see that people don’t suffer the way he suffered.”