Background and purpose: Immune therapy against amyloid-β appears to be a promising target in Alzheimer disease. However, a dose-related risk for ARIA on FLAIR images thought to represent parenchymal vasogenic edema or sulcal effusion (termed "ARIA-E"), has been observed in clinical trials. To assess the intensity of ARIA-E presentation, an MR imaging scale that is both reproducible and easily implemented would assist in monitoring and evaluating this adverse event.
Materials and methods: On the basis of a review of existing cases from a phase II bapineuzumab study, a scale was constructed with a 6-point score for the 6 regions on each side of the brain (range, 0-60). Scores would be obtained for both parenchymal and sulcal hyperintensities and frequently co-occurring gyral swelling. Inter-rater reliability between 2 neuroradiologists was evaluated in 20 patients, 10 with known ARIA-E and 10 without, by using the intraclass correlation coefficient.
Results: The 2 raters had excellent agreement in the identification of ARIA-E cases. A high inter-rater agreement was observed for scores of parenchymal hyperintensity (ICC = 0.83; 95% CI, 48-96) and sulcal hyperintensity (ICC = 0.89; 95% CI, 63-97) and for the combined scores of the 2 ARIA-E findings (ICC = 0.89; 95% CI, 62-97). Gyral swelling scores were observed to have lower inter-rater agreement (ICC = 0.54; 95% CI, -0.06-0.86).
Conclusions: The proposed rating scale provides a reliable and easily implemented instrument to grade ARIA-E imaging findings. We currently do not recommend including swelling.