Sniffin’ Sticks test in evaluating olfactory function in Parkinson’s disease

Objective To evaluate the olfactory function and its influence factors by using Sniffin’ Sticks test, and to compare the quality of Parkinson’s disease (PD) recognition between Sniffin’ Sticks and 16 kinds of odor identification in Sniffin’ Sticks(SS-16) tests. Methods The Sniffin’Sticks test was used to assess the olfactory function of 68 PD patients and 76 healthy volunteers, and the relationship between smell and age, disease duration, Unified Parkinson’s Disease Rating Scale score, Hoehn-Yahr (H-Y) rating, and cognitive function level (Montreal Cognitive Assessment) was analyzed. Results （1）The prevalence of olfactory dysfunction in PD group (83.3%) was significantly higher than that in control group (21.2%). The Sniffin’ Sticks test showed that the odor threshold score （6.6±3.2, P=0.000）, odor discrimination score （6.6±3.3, P=0.000）, 16 kinds of odor identification score （6.8±2.4, P=0.000) in PD group were significantly lower than those in control group. （2）When comparing the PD cases and healthy controls in recognition, the sensitivity and the specificity of the Sniffin’ Sticks test were 0.897 and 0.737, respectively, similar to the SS-16 test. However, the Sniffin’ Sticks test showed advantage compared with odor threshold and odor discrimination. （3）The olfactory score in PD group was positively correlated with cognitive function (r=0.243, P=0.046), and was unrelated with age, gender, disease duration, and disease severity. The olfactory score in control group was negatively correlated with age (r=-0.270, P=0.018), but positively correlated with cognitive function (r=0.281, P=0.014). Conclusions There is a higher incidence of olfactory dysfunction in PD patients than in control group. Sniffin’ Sticks test is superior to SS-16 test in quantitative and qualitative analysis of olfactory function in PD patients. Two tests both have high sensitivity and specificity in the recognition of PD. Key words: Parkinson’s disease; Smell; Olfactory disorders; Sensory thresholds; Odors