[99mTc] TRODAT-1 SPECT imaging correlates with odor identification in early Parkinson disease

Background: In vivo imaging of the dopamine transporter with [Tc-99m] TRODAT-1 (TRODAT) and olfactory testing have both been proposed as potential biomarkers in Parkinson disease (PD). Objective: To evaluate the relationship between TRODAT SPECT imaging, odor identification skills, and motor function in patients with early PD. Methods: Twenty-four patients with a clinical diagnosis of early-stage PD (mean Hoehn & Yahr stage = 1.4) underwent TRODAT imaging, Unified PD Rating Scale (UPDRS) ratings of motor function, and administration of the University of Pennsylvania Smell Identification Test (UPSIT). Brain images were obtained using a standardized processing protocol and specific uptake ratios for striatal regions of interest were calculated. Partial correlations between the imaging indices, disease duration, UPSIT scores, and UPDRS motor scores were then calculated. Results: UPSIT scores were correlated with TRODAT uptake in the striatum as a whole (r = 0.66, p = 0.001). The putamen showed the strongest correlation with the UPSIT (r = 0.74; p = 0.001). The correlation between dopamine transporter density in the caudate and UPSIT was moderate (r = 0.36, p = 0.11), but was not significant. Conclusions: Olfactory function is highly correlated with dopamine transporter imaging abnormalities in early Parkinson disease (PD). Further studies are warranted to determine whether changes over time in these two measures are also correlated in early PD.