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Optimizing Effect Sizes With Imaging Enrichment and Outcome Choices for Mild Alzheimer Disease Clinical Trials

Chang, Timothy S. MD, PhD; Teng, Edmond MD, PhD; Elashoff, David PhD; Grill, Joshua D. PhDfor the Alzheimer’s Disease Neuroimaging Initiative

Alzheimer Disease & Associated Disorders: January-March 2017 - Volume 31 - Issue 1 - p 19–26
doi: 10.1097/WAD.0000000000000150
Original Articles

Recent clinical trials in mild Alzheimer disease (AD) have enriched for amyloid-specific positron emission tomography (PET) imaging and used extended versions of the AD Assessment Scale-Cognitive Subscale (ADAS-Cog) in an effort to increase the sensitivity to detect treatment effects. We used data from mild AD participants in the AD Neuroimaging Initiative to model trial effect sizes for 12- and 24-month trials using 3 versions of the ADAS-Cog and increased standardized uptake value ratio (SUVR) cutoffs for amyloid imaging inclusion criteria. For 12-month trials, extended ADAS-Cog versions improved effect sizes. The ADAS-Cog11 elicited larger effect sizes when enriching for SUVR 1.1 only, whereas the ADAS-Cog12 and ADAS-Cog13 were associated with larger effect sizes with higher SUVR thresholds. For 24-month trials, extended ADAS-Cog versions increased effect sizes for trials not enriched for amyloid and trials enriched for SUVR 1.1. Only enriching for higher SUVR thresholds (1.3 and 1.4, not 1.1) increased trial power. We conclude that extended versions of the ADAS-Cog improve mild AD trial effect sizes for both 12- and 24-month long studies, whereas amyloid imaging criteria may be most valuable for 12-month trials.

Departments of *Neurology

Biostatistics, David Geffen School of Medicine, University of California, Los Angeles

Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles

§Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, Irvine, CA

Data used in preparation of this article were obtained from the Alzheimer’s Disease Neuroimaging Initiative (ADNI) database ( As such, the investigators within the ADNI contributed to the design and implementation of ADNI and/or provided data but did not participate in analysis or writing of this report. A complete listing of ADNI investigators can be found at:

J.D.G. and E.T. were supported by NIA AG016570. J.D.G. is currently supported by NIA AG016573. Data collection and sharing for this project was funded by the Alzheimer’s Disease Neuroimaging Initiative (ADNI) (National Institutes of Health Grant U01 AG024904) and DOD ADNI (Department of Defense award number W81XWH-12-2-0012). ADNI is funded by the National Institute on Aging, the National Institute of Biomedical Imaging and Bioengineering, and through generous contributions from the following: Alzheimer’s Association; Alzheimer’s Drug Discovery Foundation; Araclon Biotech; BioClinica Inc.; Biogen Idec Inc.; Bristol-Myers Squibb Company; Eisai Inc.; Elan Pharmaceuticals Inc.; Eli Lilly and Company; EuroImmun; F. Hoffmann-La Roche Ltd and its affiliated company Genentech Inc.; Fujirebio; GE Healthcare; IXICO Ltd; Janssen Alzheimer Immunotherapy Research & Development, LLC; Johnson & Johnson Pharmaceutical Research & Development, LLC; Medpace Inc.; Merck & Co. Inc.; Meso Scale Diagnostics, LLC; NeuroRx Research; Neurotrack Technologies; Novartis Pharmaceuticals Corporation; Pfizer Inc.; Piramal Imaging; Servier; Synarc Inc.; and Takeda Pharmaceutical Company. The Canadian Institutes of Health Research is providing funds to support ADNI clinical sites in Canada. Private sector contributions are facilitated by the Foundation for the National Institutes of Health ( The grantee organization is the Northern California Institute for Research and Education, and the study is coordinated by the Alzheimer’s Disease Cooperative Study at the University of California, San Diego. ADNI data are disseminated by the Laboratory for Neuro Imaging at the University of Southern California.

The authors declare no conflicts of interest.

Reprints: Joshua D. Grill, PhD, Institute for Memory Impairments and Neurological Disorders, University of California, Irvine, 3206 Biological Sciences III, Irvine, CA 92697-4545 (e-mail:

Received December 4, 2015

Accepted March 8, 2016

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