1. Division of Gastroenterology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
2. Department of Statistical Science, Duke University, Durham, NC, USA
3. Center for Gastrointestinal Biology and Disease, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
4. Department of Statistics, University of North Carolina, Chapel Hill, NC, USA
5. Multidisciplinary Center for Inflammatory Bowel Diseases, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA