David S Goldberg1, Michael Charlton2. 1. Division of Gastroenterology, Department of Medicine, Center for Clinical Epidemiology and Biostatistics, Department of Biostatistics and Epidemiology, Perelman School of Medicine and Leonard Davis Institute of Health Economics, University of Pennsylvania, Philadelphia, Pennsylvania. Electronic address: david.goldberg@uphs.upenn.edu. 2. Division of Hepatology, Department of Medicine, Intermountain Medical Center, St. Murray, Utah.