To examine if differences exist in [¹²³I] ioflupane dopamine transporter (DAT) binding between African Americans and Caucasians with normal presynaptic dopaminergic function. 

¹²³I] ioflupane- single photon emission computed tomography (SPECT) has been widely used in the assessment of presynaptic dopaminergic function. Studies in healthy volunteers found that age and sex may affect [¹²³I] ioflupane DAT binding; however, the effects of another demographic variable, ethnicity, on [¹²³I] ioflupane binding have not been well studied.

A retrospective chart review study was conducted for individuals with [¹²³I] ioflupane-SPECT done in a single academic center from January 2012 to July 2022. All image studies were visually inspected and interpreted as normal or abnormal presynaptic dopaminergic function. Only subjects with normal presynaptic dopaminergic function (n=270) were included in this analysis. Quantitative measurements of [¹²³I] ioflupane-specific binding ratios (SBR) were computed using DaTQUANT software (GE Healthcare). SBRs of bilateral striatum and sub-regions of bilateral caudate nucleus, anterior and posterior putamen were compared between African Americans and Caucasians by using multiple linear regression analysis adjusted for age and sex.

Among the 270 subjects with normal presynaptic dopaminergic function, African Americans (n=92, mean age 66.5) were younger than the Caucasians (n=178, mean age 69.0) (p=0.035), and the percentage of female subjects in the African American group was slightly higher than in the Caucasian group (50% vs. 43.3%, p>0.05).  After adjusting for age and sex, African Americans had higher [¹²³I] ioflupane uptakes as measured by SBRs in right striatum (β=0.182, 95%CI: 0.056, 0.308; p=0.005), left striatum (β=0.202, 95%CI: 0.075, 0.329; p=0.002) and in all the sub-regions, compared to Caucasians. 

We observed differences of [¹²³I] ioflupane binding between African Americans and Caucasians with normal presynaptic dopaminergic dysfunction. Future studies are needed to examine whether and how ethnicity affects DAT binding activities and its clinical relevance.