There are plenty of online articles claiming that a woman called Joy Milne is able to tell whether someone has Parkinson disease by smell:
A British woman who can smell Parkinson’s disease has helped scientists discover 10 molecules linked to the condition which could lead to the first diagnostic test.
Researchers at Manchester University first began to believe Parkinson’s might have a discernible odour when Joy Milne of Perth, Scotland, claimed she detected a change in the odour of her husband Les six years before he was diagnosed with the condition.
Mrs Milne, 67, claimed her husband’s smell changed subtly years before any difficulty with movement started to emerge. Mr Milne died in 2015 aged 65.
When researchers conducted tests with Mrs Milne they found she was able to identify people living with Parkinson’s from people without the condition by smelling skin swabs taken from both groups.
-"Woman who can smell Parkinson's disease helps scientists develop first diagnostic test", The Telegraph (2017-12-18)
"Meet the woman who can smell Parkinson's disease", The Telegraph (2017-12-19)
"This Woman Can Smell Parkinson's Disease", Independent (2017-12-18)
Is it true?
Is there any evidence suggesting that Joy Milne can smell Parkinson's disease?