# Multicenter development and validation of a probability-based model to diagnose Lewy body disease using ¹²³I-meta-iodobenzylguanidine

## TL;DR

A probability-based model using 123I-mIBG imaging reliably distinguishes Lewy body disease from other conditions across multiple centers.

## Contribution

The model was validated across Japanese and European institutions, confirming its real-world applicability.

## Key findings

- The model achieved AUCs of 0.880 and 0.899 for early and late H/M ratios in diagnosing LBD.
- Late-phase imaging improved diagnostic accuracy in intermediate probability cases.
- Coronary artery disease reduced the model's diagnostic performance.

## Abstract

We previously proposed that a probability-based sympathetic 123I-meta-iodobenzylguanidine (mIBG) index (SMILe) could distinguish the presence or absence of Lewy body disease (LBD) based on findings at a single center. However, whether the model would be useful in the real world remained uncertain. Therefore, we updated and evaluated its performance at five Japanese and three European institutions.

We compared data from 967 patients with suspected LBD with 62 controls from a normal database (NDB). Of 815 patients with guideline-based diagnoses, 483 had LBD (Parkinson disease [PD] or dementia with Lewy bodies [DLB]) and 332 did not have LBD. Heart-to-mediastinum (H/M) ratios were standardized using a phantom-based method. Logistic regression models included early and late H/M ratios, age, sex, and comorbidities. We assessed diagnostic performance using ROC analysis and cross-validation.

The updated model discriminated LBD from other diseases (AUC for early and late H/M, 0.880 0.899, respectively). Age correction of H/M ratios based on the NDB did not improve accuracy. Median early H/M ratios [SMILe probability] were 3.09 [12.8%] for NDB, 2.57 [37.5%] for Alzheimer disease, 1.76 [84.7%] for PD, and 1.62 [89.0%] for DLB, with significantly lower H/M ratios and higher probabilities in PD and DLB compared with controls (p < 0.0001). Late-phase imaging added value mainly in intermediate borderline (30%–70%) situations. Coronary artery disease attenuated the diagnostic performance of SMILe.

The probability-based 123I-mIBG model reliably differentiated LBD from other diseases. Standardization among sites supports global applicability and reflects real-world clinical practice.