123I-MIBG scintigraphy utility and cut-off value in a clinically representative dementia cohort

Abstract Objective To determine the utility of 123 I-metaiodobenzylguanidine cardiac scintigraphy (MIBG), and optimum heart: mediastinum ratio (HMR) for differentiating dementiawith Lewy bodies(DLB) from Alzheimer's disease (AD) in a clinically representative population, comparing findings with those of 123 I-2β -carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (FP-CIT) SPECT. Methods We recruited subjects with probable DLB (n = 17) and probable AD (n = 16) from clinical services. Each participant underwent clinical examination, cardiac MIBG scintigraphy and FP-CIT SPECT. Diagnosis was made on the basis of clinical symptoms using validated criteria. Cardiac MIBG uptake was measured by the planar HMR, blind to clinical diagnosis, with values below a cut-offtaken from a previous study ( Results MIBG had a sensitivity, specificity and overall accuracy of 71%, 81% and 76% for distinguishing DLB from AD. FP-CIT demonstrated a sensitivity, specificity and accuracy of 82%, 88% and 85%. Using a lower HMR cut-offto distinguish between abnormal and normal MIBG scans improved the accuracy of MIBG, raising specificity (100%) and overall accuracy (85%) without compromising sensitivity (71%). Neither prescription of potentially interfering medications, nor a history of myocardial infarction (MI), had a significant effect on HMR. Conclusion We found that MIBG did not demonstrate superior sensitivity and overall accuracy to FP-CIT. HMR cut-offinfluences biomarker utility, and clinical and Caucasian populations may require a lower cut-offthan those reported elsewhere. Future MIBG studies should include clinically representative cohorts as neither medications nor previous MI appear to influence HMR.