1. Division of Gastroenterology and Hepatology, University of Colorado, Anschutz Medical Campus, Aurora, Colorado
2. Department of Preventive Medicine, Division of Biostatistics
3. Division of Gastroenterology and Hepatology, University of Washington, Seattle, Washington, USA
4. Digestive Physiology, Hospices Civils de Lyon and Lyon I University, Lyon, France
5. Division of Gastroenterology & Hepatology, Northwestern University, Chicago, Illinois