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 100050, PR China
2. Department of Gastroenterology, Beijing University of Chinese Medicine Third Affiliated Hospital, Beijing 100029, PR China
3. Department of Gastroenterology, Ordos Central Hospital, National Clinical Research Center for Digestive Disease-Ordos Subcenter, Ordos 017000, Innermongolia, PR China