1 Division of Gastroenterology and Hepatology, Department of Medicine, Stanford University School of Medicine, Stanford, California.
2 VA San Diego Healthcare System, Division of Gastroenterology, Department of Internal Medicine, Moores Cancer Center, University of California San Diego, San Diego, California.
3 Division of Gastroenterology, Hepatology and Nutrition and, Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania.