1. Department of Veterans Affairs Center for Clinical Management Research, Ann Arbor, MI, USA
2. Division of Gastroenterology, University of Michigan, Ann Arbor, MI, USA
3. Department of Internal Medicine, University of Michigan, Ann Arbor, MI, USA
4. Department of Statistics, University of Michigan, Ann Arbor, MI, USA
5. Department of Pathology, University of Michigan, Ann Arbor, MI, USA