1. Department of Gastroenterology, Beijing Friendship Hospital, Capital Medical University, National Clinical Research Center for Digestive Disease, Beijing Digestive Disease Center, Beijing Key Laboratory for Precancerous Lesion of Digestive Disease, Beijing, China;
2. Department of Gastroenterology, Beijing Shijingshan Hospital, Teaching Hospital of Capital Medical University, Beijing, China;
3. Department of Gastroenterology, The First People's Hospital of Yunnan Province, The Affiliated Hospital of Kunming University of Science and Technology, Kunming, Yunnan, China;
4. Department of Gastroenterology, Beijing Xuanwu Hospital, Capital Medical University, Beijing, China.