1. Department of Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA;
2. Division of Gastroenterology and Hepatology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA;
3. Leonard Davis Institute of Health Economics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA;
4. Department of Biostatistics, Epidemiology, and Informatics, University of Pennsylvania, Philadelphia, Pennsylvania, USA;
5. Section of Digestive Diseases, Yale School of Medicine, New Haven, Connecticut, USA;
6. VA Connecticut Healthcare System, West Haven, Connecticut, USA;
7. Gastroenterology Section, Corporal Michael J. Crescenz VA Medical Center, Philadelphia, Pennsylvania, USA.