1. Biostatistics Unit, Group Health Research Institute, Seattle, WA, USA
2. Department of Biostatistics, University of Washington, Seattle, WA, USA
3. Department of Biostatistics & Bioinformatics, Duke University School of Medicine, Durham, NC, USA
4. Duke Clinical Research Institute, Durham, NC, USA
5. Office of Disease Prevention, Division of Program Coordination Planning and Strategic Initiatives, Office of the Director, National Institutes of Health, Bethesda, MD, USA
6. Kaiser Permanente Center for Health Research, Portland, OR, USA