1. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia2Division of Gastroenterology, University of Pennsylvania, Philadelphia.
2. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia3Abramson Cancer Center, University of Pennsylvania, Philadelphia
3. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia4Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia
4. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia
5. Department of Dermatology, University of Pennsylvania, Philadelphia
6. Department of Epidemiology, University of Alabama at Birmingham
7. Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham
8. Division of Gastroenterology, University of Pennsylvania, Philadelphia.
9. Center for Clinical Epidemiology and Biostatistics, University of Pennsylvania, Philadelphia5Department of Dermatology, University of Pennsylvania, Philadelphia
10. Department of Epidemiology, University of Alabama at Birmingham7Division of Clinical Immunology and Rheumatology, University of Alabama at Birmingham