Scientists in the UK have developed a test to determine whether people have Parkinson’s disease — thanks to the help of a woman who can sniff out the disorder.

Joy Milne, a retired nurse from Scotland, knew her husband Les had Parkinson’s over a decade before he was diagnosed when she identified a change in the way he smelled.

“He had this musty rather unpleasant smell especially round his shoulders and the back of his neck and his skin had definitely changed,” Joy Milne said. “I kept saying to him, you’re not showering properly. And he became quite angry about it at first,” she told Sky News.

Joy connected the smell to the disease after Les was diagnosed, and the couple met people at a Parkinson’s support group who had the same smell, reports the BBC. According to the Daily Mail, she has been found to have hereditary hyperosmia – a heightened sensitivity to smells.

Now, academics at the University of Manchester — working with Joy — have made a breakthrough by developing a test that can identify people with Parkinson’s disease. The test uses a simple cotton swab run along the back of the neck. The researchers claim the test is 95% accurate under laboratory conditions.

By working with Joy, scientists found that sebum — an oily substance secreted from pores in the skin – contained ten compounds linked to Parkinson’s. They also discovered that the most accurate results came from sebum taken from the back of people’s necks and between their shoulder blades.

Dr. Perdita Barran, who led the research, said of Joy’s contribution, “If Joy didn’t exist, I don’t think any of this would have happened – not just because of her nose, but because of her persistence in thinking her ability could help people. I was skeptical at first, but she has been proven right.”

Dr. Barran believes the work done by her team could be transformative. “At the moment we have developed it in a research lab and we are now working with colleagues in hospital analytical labs to transfer our test to them so that it can work within an NHS environment,” Barran said. “We are hoping within two years to be able to start to test people in the Manchester area.”

Les Milne, a retired doctor, died in 2015.

Joy said, “I promised my husband the night before he died that I would help with research on Parkinson’s until there is a test for this cruel disease. I feel lucky that I have this ability, to help people with early diagnosis.”

Currently, there is no cure and no definitive diagnostic test for Parkinson’s, considered the fastest-growing neurological condition in the world. Doctors diagnose patients by observing symptoms.