Amyloid status imputed from a multimodal classifier including structural MRI distinguishes progressors from nonprogressors in a mild Alzheimer's disease clinical trial cohort.

Introduction: Mild-Alzheimer's disease (AD) subjects without significant AO pathology represent a confounding finding for clinical trials because they may not progress clinically on the expected trajectory, adding variance into analyses where slowing of progression is being measured. Methods: A prediction model based on structural magnetic resonance imaging (MRI) in combination with baseline demographics and clinical measurements was used to impute A beta status of a placebo-treated mild-AD sub-cohort (N = 385) of patients participating in global phase 3 trials. The clinical trajectories of this cohort were evaluated over 18 months duration of the trial, stratified by imputed A beta status within a mixed-model repeated measures statistical framework. Results: In the imputed A beta-positive cohort, both cognitive (ADAS-Cog(14) and MMSE) and functional (ADCS-iADL) measures declined more rapidly than in the undifferentiated population. Discussion: Our results demonstrate imputing AP status from MRI scans in mild-AD subjects may be a useful screening tool in global clinical trials if amyloid measurement is not available. (C) d2016 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.