Affiliation: | 1. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, , Philadelphia, PA, USA;2. Department of Biostatistics and Epidemiology, University of Pennsylvania, , Philadelphia, PA, USA;3. Division of Hematology/Oncology, University of Pennsylvania, , Philadelphia, PA, USA;4. Division of Gastroenterology, University of Pennsylvania, , Philadelphia, PA, USA |