Predictive value of the smell identification test for nigrostriatal dopaminergic depletion in Korean tremor patients

Background: The predictive value of Cross-Cultural Smell Identification Test for nigrostriatal dopaminergic depletion in Korean tremor patients has yet to be assessed. Methods: Three hundred nineteen drug-naive patients who visited our clinic for the diagnosis of their tremor, and took both Cross-Cultural Smell Identification Test and dopamine transporter PET were included in the data analysis. Visual grading of each PET image was performed by two independent neurologists. Results: Smell test scores were significantly correlated to the striatal dopaminergic activity (Kendall's τb=-0.291, p<0.001). However, smell test score alone appeared to have relatively weak power for predicting dopaminergic depletion (area under the curve=0.693). Multivariate logistic regression model with inclusion of the patient's age and symptom duration as independent variables enhanced predictive power for dopaminergic depletion (area under the curve=0.812). Conclusions: These results demonstrated that Cross-Cultural Smell Identification Test measurements alone may be insufficient to predict striatal dopaminergic depletion in Korean tremor patients.