Objective: To compare the olfactory function of Parkinson’s disease (PD) patients and healthy controls by using an olfactory screening test composed of common spices. In addition, we wanted to determine the impact of disease duration and cognitive impairment on the olfactory function in PD patients.

Background: Worsening of the ability to smell is one of the earliest non-motor symptoms of PD.

Methods: We included 30 PD patients (mean age of 68.8 years, average disease duration of 5.0 years) and 30 healthy controls matched for age and gender. MoCA was used for cognitive testing.

The olfactory test consisted of 10 spices (Kotanyi, Ltd.): coffee, anise, caraway, basil, marjoram, cinnamon, cloves, rosemary, thyme and oregano. We put all the spices in 2 identical sets of containers covered with the perforated lids. Subjects were asked to smell from one container from the first set and find the identical smell in the second set. We returned the selected container to the second set and changed its position for the next trial. Subjects were not informed if the answer was correct or not. One point was given for each correct answer.

Results: There was a statistically significant difference in the number of correct answers between PD patients (mean score = 2.23) and controls (mean score = 5.20) (U = 133.5, p<0.001).  43% of PD patients correctly detected only one or none of the presented spices, and only 3% of the controls had such a low result. All of the healthy controls correctly detected pairs of coffee containers, but only 47 % of PD patients could do the same. The combination of five selected spices (coffee, cloves, marjoram, cinnamon, caraway) showed the best discrimination between two groups (sensitivity = 80% and specificity = 80%). There was a weak positive correlation between olfactory and cognitive dysfunction in PD patients (ρ = 0.36, p<0.001). The correlation between disease duration and olfactory function (ρ = -0.10, p>0.05) was not statistically significant, but showed a negative trend between these two variables.

Conclusions: A simple “home made” olfactory test composed of only five selected spices, could detect the olfactory dysfunction in 80% of our PD patients. This result is consistent with the previous studies showing 75-90% of PD patients having olfactory dysfunction (1,2). 

References: 1. Doty RL. Olfaction in Parkinson’s disease and related disorders. Neurobiol Dis 2012;46:527‐552.

2. Haehner A, Boesveldt S, Berendse HW, et al. Prevalence of smell loss in Parkinson’s disease—a  multicenter study. Parkinsonism Relat Disord 2009;15:490‐494. 

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MDS Abstracts - https://www.mdsabstracts.org/abstract/home-made-olfactory-spice-discrimination-test-for-pd/