To explore if differences exist in [¹²³I] ioflupane Dopamine transporter (DAT) binding between African-Americans and Caucasians with and without presynaptic dopaminergic deficit.

Racial disparities exist among patients with common movement disorders such as Parkinson disease (PD) and essential tremor (ET). PD and ET are more common in Caucasians than in non-Caucasians, particularly in African-Americans. However, the underlying mechanisms of the above racial differences remain unknown.

Retrospective chart review was performed of consecutive patients with tremor and/or Parkinsonian syndrome who had undergone a [¹²³I] ioflupane SPECT imaging in a single academic medical center. All images were visually inspected and graded by a certified Nuclear Radiologist as normal or abnormal presynaptic dopaminergic function. Quantitative [¹²³I] ioflupane uptake was measured by specific binding ratios (SBR) computed by DaTQUANT software (GE Healthcare). SBRs of bilateral striatum and its sub-regions (caudate, anterior putamen and posterior putamen) were compared between African-Americans and Caucasians by using multiple linear regression analysis adjusted for age, sex, and abnormal scan status. Interaction terms were tested to determine if race effects were moderated by abnormal scan status.

Compared to Caucasians (n=173, mean age 68.2±9.9, 36% female and 43% with abnormal scan), African Americans (n=82, mean age 65.7±9.3, 44% female and 39% with abnormal scan) had higher [¹²³I] ioflupane uptake as measured by SBRs in right striatum (β=0.123, 95%CI: 0.005, 0.242; p=0.041), left striatum (β=0.163, 95%CI: 0.039, 0.286; p=0.01) and in its sub-regions of right caudate (β=0.186, 95%CI: 0.042, 0.330; p=0.012), left caudate (β=0.212, 95%CI: 0.061, 0.362; p=0.006) and right posterior putamen(β=0.099, 95%CI: 0.002, 0.195; p=0.045). Race by abnormal scan status interactions were not statistically supported for any models.

We observed differences of [¹²³I] ioflupane DAT binding between African-Americans and Caucasians independent of presynaptic dopaminergic dysfunction status. Racial differences and the underlying mechanisms of tremor and Parkinsonian syndrome warrant further study.