1. Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, USA;
2. White River Junction VAMC, White River Junction, Vermont, USA;
3. New Hampshire Colonoscopy Registry, Lebanon, New Hampshire, USA;
4. University of Connecticut, Storrs, Connecticut, USA;
5. Division of Gastroenterology and Hepatology, Department of Medicine, Indiana University School of Medicine, Indianapolis, Indiana, USA;
6. Department of Gastroenterology and Hepatology, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire, USA.