1. Department of Gastroenterology and Hepatology, Graduate School of Medical Sciences; Kumamoto University; Kumamoto Japan
2. Oda GI Endoscopy and Gastroenterology Clinic; Kumamoto Japan
3. Department of Gastroenterology; Minamata City General Hospital & Medical Center; Kumamoto Japan
4. Hattori GI Endoscopy and Oncology Clinic; Kumamoto Japan
5. Department of Medical Statistics; Toho University; Tokyo Japan