Objective: To assess the olfactory performance in patients with PD using “Sniffin’ Sticks”.

Background: Olfactory dysfunction is an important early premotor biomarker for PD, and olfactory examination can be a key screening test to identify individuals at high risk for PD developing. However, the diagnostic value of the detection of hypo- and anosmia requires clarification.

Method: 2 groups: 1^st – patients with PD (n=111) and 2^nd – a control group (n=32 healthy volunteers) were formed in a prospective randomized study. The olfactory performance was assessed using the extended “Sniffin’ Sticks” test. Three parameters: olfactory threshold (T), odor identification (I) and odor discrimination (D) were determined. The maximum number of points that patient could score at each stage was 16, and in the general test – 48 (TDI-index=48).

Results: Hypo- or anosmia was observed in 87% of PD cases (violation of olfactory threshold – 77% and odor identification – 80%, table1). Olfactory dysfunction in PD was more pronounced in men (TDI-index – 16,8±2,7 points) compared with women (22,6±4,2, p<0,05).
Olfactory predictors of PD, according to the ROC analysis, were olfactory threshold – less than 4,0 (sensitivity 79,5% and specificity 69,75%); odor discrimination – less than 11,0 (70,6% and 78,5%, respectively); and the most effective – odor identification test – less than 13,0 (89,6% and 81,1%, respectively).
The level of olfaction in PD did not correlate with either the duration and the functional stage of the disease (table 2, p>0,05). The most pronounced impairment of olfaction in all modalities occurred in mixed and akinetic-rigid subtypes of PD, while the olfaction was more preserved in patients with a tremor-dominant PD (p<0,05).

Conclusion: Proposed quantitative indicators of olfactory tests (olfactory threshold, odors discrimination and identification) with high sensitivity and specificity can be used as additional non-motor diagnostic criteria for PD, but not applicable for monitoring the pathological process.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/diagnostic-value-of-olfactory-dysfunction-in-parkinsons-disease/