This retrospective review of 695 patients shows that medications and comorbidities that can confound cardiac 123I‑MIBG scintigraphy are common (55.3%), frequently limiting the test's interpretability in routine clinical practice.

By documenting the high prevalence of factors that reduce MIBG reliability, the study signals the need for careful patient selection and protocol adjustments when using MIBG as a diagnostic biomarker or for stratifying patients in PD research and trials.

BACKGROUND: Reduced cardiac uptake on 123Iodine-metaiodobenzylguanidine (MIBG) scintigraphy is a valuable tool for differentiating neurodegenerative parkinsonism but interpretation can be difficult due to comorbidities and drug-tracer interactions. OBJECTIVES: This study investigated factors limiting the clinical applicability of MIBG scintigraphy in everyday clinical practice. METHODS: Patient records (2021-2022) were retrospectively reviewed, independent of whether MIBG scintigraphy was performed, for comorbidities and concomitant medication confounding its interpretation. RESULTS: Six hundred ninety five patients (640 Parkinson's disease, 22 multiple system atrophy, 33 progressive supranuclear palsy) were included. Factors potentially influencing cardiac MIBG binding were present in 55.3% with 18.1% exhibiting multiple factors. Medications with known drug-tracer interactions were found in 46.9% and comorbidities associated with reduced cardiac MIBG uptake in 20.9%. CONCLUSIONS: The clinical utility of MIBG scintigraphy is frequently restricted by medications and comorbidities highlighting the need of careful planning in clinical practice.