1. Department of Medicine, Hospital of University of Pennsylvania, Philadelphia, Pennsylvania, USA
2. Department of Gastroenterology and Hepatology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
3. Department of Biostatistics, Epidemiology and Informatics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
4. Leonard Davis School of Healthcare Economics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA