1. Department of Gastroenterology, The Second Hospital of Hebei Medical University, Shijiazhuang, China
2. Department of Gastroenterology, Handan Central Hospital, Handan, China
3. Department of Gastroenterology, The Third Hospital of Hebei Medical University, Shijiazhuang, China
4. Department of Gastroenterology, The First Hospital of Handan, Handan, China
5. Digestive Endoscopy Center, The First Affiliated Hospital of Hebei North. University, Zhangjiakou, China.