1. Division of Gastroenterology and Hepatology, University of Michigan Medicine , Ann Arbor, MI , USA
2. Department of Health Behavior and Health Education, University of Michigan School of Public Health , Ann Arbor, MI , USA
3. VA Center for Clinical Management Research, VA Ann Arbor Health care System , Ann Arbor, MI , USA
4. Division of Gastroenterology and Hepatology, University of Texas Southwestern Medical Center , Dallas, TX , USA
5. Department of Statistics, University of Michigan , Ann Arbor, MI , USA