Validation of an MRI Rating Scale for Amyloid-Related Imaging Abnormalities.

INTRODUCTION: Immunotherapeutic agents against amyloid beta (Aβ) are associated with adverse events, including amyloid-related imaging abnormalities with edema and effusion (ARIA-E). Recently, a magnetic resonance imaging (MRI) rating scale was developed for ARIA-E detection and classification. The aim of this study was to validate the use of this rating scale in a larger patient group with multiple raters.

METHODS: MRI scans of 75 patients (29 with known ARIA-E and 46 control subjects) were analyzed by five neuroradiologists with different degrees of expertise, according to the ARIA-E rating scale. For each patient, we included a baseline and a follow-up fluid-attenuated inversion recovery image. Interrater agreement was calculated using intraclass correlation coefficient (ICC).

RESULTS: On average, 4.1% of the ARIA-E cases were missed. We observed a high interrater agreement for scores of sulcal hyperintensity (SH; ICC = .915; 95% CI 85-95) and for the combined scores of the 2 ARIA-E findings, parenchymal hyperintensity (PH) and SH (ICC = .878; 95% CI 79-93). A slightly lower agreement for PH (ICC = .678; 95% CI 51-81) was noted.

CONCLUSION: The ARIA-E rating scale is a simple tool to evaluate the extent of ARIA-E in patients recruited into Aβ-lowering therapeutic trials. It shows high interrater agreement among raters with different degrees of expertise.