1. Kaiser Permanente of Washington Health Research Institute (formerly Group Health Research Institute), Seattle, WA, USA
2. Division of Gastroenterology, Hepatology, and Nutrition, Department of Medicine and Epidemiology, University of Pittsburgh, Pittsburgh, PA, USA
3. Division of Gastroenterology, Beth Israel Deaconess Medical Center, Boston, MA, USA
4. Department of Biomedical Informatics, University of Pittsburgh, Pittsburgh, PA, USA
5. Department of Health Care Policy, Harvard Medical School, Boston, MA, USA
6. Division of Gastroenterology and Hepatology, University of North Carolina School of Medicine, Chapel Hill, NC, USA,
7. Division of General Internal Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA