Can Dogs Detect Parkinson’s Disease by Smell?

Humans’ Best Friends —⁠ and Diagnostic Partners

Dogs excel in many tasks: detecting drugs, explosives, criminals, finding disaster victims, assisting people with disabilities, providing therapeutic support, and even recognizing certain medical conditions —⁠ from prostate cancer to malaria or COVID-19. Parkinson’s disease is another condition where early diagnosis is challenging due to the absence of reliable clinical biomarkers.

Although laboratory tests can reach up to 98% accuracy, they are not yet widely implemented in clinical practice. Similarly, highly accurate SPECT scans are rarely used in primary diagnosis. Researchers therefore asked whether dogs could identify PD by detecting one of its prodromal symptoms —⁠ seborrheic dermatitis —⁠ via skin odor.

How the Study Was Conducted

This was a prospective, randomized, double-blind study using 305 skin swab samples —⁠ 130 from 40 patients with PD (57.5% male) who were not yet taking PD medications, recruited from 25 NHS centers, and 175 from matched controls (companions of patients or volunteers from the Medical Detection Dogs center). Median patient age was 71 years, median disease duration 2 years, and most were non-smokers.

Controls were matched by age, BMI, sex, and smoking status. Ten dogs underwent initial training; two were selected for full testing: a 2-year-old golden retriever (Dog 1) and a 3-year-old Labrador × golden retriever (Dog 2). Both were professionally trained following a standardized protocol. Prior to testing, dogs were trained using samples from newly diagnosed PD patients, healthy individuals, and patients with other neurological diseases.

Of the 305 samples, 205 were used for training and 100 for blinded testing (40 PD-positive, 60 controls). Each sample was split into duplicate halves —⁠ both used for training or one used as a “dummy” filler during testing.

Dogs were presented with samples in rows of four, containing at most one positive sample (sometimes none). Each line could be examined up to four times. Dogs’ behaviors were coded as indication, hesitation, interest, no interest, or not located; only a clear “indication” counted as a positive result.

When the handler was confident in the dog’s choice, they reported it to the blinded experimenter, who logged the result and revealed whether it was correct —⁠ prompting a reward. Calibration checks were allowed at any time.

High Sensitivity and Specificity

Both dogs successfully distinguished PD-positive samples from controls they had never encountered before. Sensitivity was high (Dog 1 : 70%, Dog 2 : 80%) —⁠ comparable to canine detection performance for malaria, and exceeding that reported for bladder cancer and other diseases. Specificity was also strong (Dog 1 : 90%, Dog 2 : 98.3%).

Agreement between the two dogs for positive samples was higher than expected by chance, suggesting that PD likely has a distinct “odor signature.”

Differences in performance between the dogs may reflect individual temperament or subtle variations in training. The researchers note that although only 2 of the original 10 dogs were deemed suitable for full training, their final performance shows that the task is learnable for dogs with the right capabilities.

A Potential Complement to Existing Diagnostic Tools

The research team concluded that early detection of biomarkers in sebum —⁠ using dogs’ exceptional olfactory sensitivity —⁠ may someday complement existing diagnostic methods. After further refinement, such an approach could support rapid screening or aid diagnosis in cases where PD is challenging to identify early.

Editorial Team, Medscope.pro

Source:

Rooney N., Trivedi D. K., Sinclair E. et al. *Trained dogs can detect the odor of Parkinson's disease.* Journal of Parkinson’s Disease 2025; 0 (0). doi: 10.1177/1877718X251342485.