Dogs can detect Parkinson's disease by odour

People with Parkinson’s disease (PD) have an odour that can be reliably detected from skin swabs by trained dogs. That’s according to new research by the Universities of Bristol and Manchester, in collaboration with charity Medical Detection Dogs, which has been published in the Journal of Parkinson’s Disease.

A definitive diagnostic test for PD remains elusive, so identification of potential biomarkers could help diagnosis and timely intervention. As noted by Claire Guest, Medical Detection Dogs CEO and Chief Scientific Officer, “There is currently no early test for Parkinson’s disease and symptoms may start up to 20 years before they become visible and persistent leading to a confirmed diagnosis.

“Timely diagnosis is key as subsequent treatment could slow down the progression of the disease and reduce the intensity of symptoms.”

A Golden Retriever named Bumper and a black Labrador named Peanut were trained by Medical Detection Dogs to distinguish between swabs of sebum (the oily substance produced by our skin) from people with and without Parkinson’s disease. The dogs were trained over a number of weeks on over 200 odour samples from individuals who had tested positive for PD and control samples from people who did not have the disease. Samples were presented to the dogs on a stand system and the dogs were rewarded for correctly indicating a positive sample and for correctly ignoring a negative sample.

In a double-blind trial, the dogs showed sensitivity of up to 80% and specificity of up to 98%. Not only that, they detected PD in samples from patients who also had other health conditions.

“Identifying diagnostic biomarkers of PD, particularly those that may predict development or help diagnose disease earlier, is the subject of much ongoing research,” said lead author Nicola Rooney, Associate Professor at Bristol Veterinary School at the University of Bristol. “The dogs in this study achieved high sensitivity and specificity and showed there is an olfactory signature distinct to patients with the disease. Sensitivity levels of 70% and 80% are well above chance and I believe that dogs could help us to develop a quick, non-invasive and cost-effective method to identify patients with Parkinson’s disease.”

In related research, scientists at The University of Manchester, in collaboration with Salford Royal NHS Trust and the Medical University of Innsbruck, have demonstrated that compounds or ‘volatiles’ found in sebum hold key biomarkers for identifying PD in its earliest stages. The work was inspired by the observations of ‘super smeller’ Joy Milne, who detected a unique scent in individuals with PD, prompting the exploration of sebum as a source of diagnostic biomarkers.

Using a technique known as Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS), the scientists analysed skin swabs from participants with PD, healthy volunteers, and those with a sleep disorder called isolated REM sleep behaviour disorder (iRBD) — a known early warning sign of PD. The results, published in npj Parkinson’s disease, showed that people with iRBD had distinct chemical profiles in their sebum that were different from healthy individuals but not yet as pronounced as those with established PD.

The study thus supports the idea that PD leaves a detectable trace on the body well before physical symptoms appear. The researchers are now continuing to develop and improve the sebum-based testing to eventually use as a practical tool in real-world clinical settings.

Image credit: Medical Detection Dogs.