1. Division of Gastroenterology & Hepatology, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA
2. Department of Medicine, Duke University School of Medicine, Durham, North Carolina, USA
3. Division of Gastroenterology & Hepatology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA
4. Leonard Davis Institute of Health Economics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania, USA