1. Division of General Internal Medicine, Department of Medicine, University of Washington, Seattle, Washington, USA.
2. Section of General Internal Medicine, Department of Medicine, University of Chicago, Chicago, Illinois, USA.
3. Division of General Internal Medicine, Department of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
4. Division of General Medicine & Clinical Epidemiology, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA.