1. Department of Internal Medicine, University of Oklahoma Health Sciences Center, 1100 N Lindsay Ave, Oklahoma City, OK 73104, USA
2. Department of Gastroenterology, Virginia Commonwealth University, Richmond, VA, USA
3. Department of Gastroenterology, SUNY Health Science Center, Brooklyn, New York, USA
4. Department of Biostatistics & Epidemiology, University of Oklahoma Health Sciences Center, 801 NE 13th St., Oklahoma City, OK, USA
5. Department of Medicine, Neurogastroenterology and Motility Program, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
6. Department of Medicine, Section of Digestive Diseases and Nutrition, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
7. Department of Medicine, Section of Digestive Diseases and Nutrition, Veterans Affairs Medical Center, Oklahoma City, OK, USA