1. Department of Gastroenterology, Peking University Ditan Teaching Hospital, Beijing 100015, P.R. China
2. Department of Gastroenterology, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, P.R. China
3. Department of Gastroenterology, Beijing Changping Hospital, Beijing 100085, P.R. China
4. Department of Center of Integrated Traditional Chinese and Western Medicine, Peking University Ditan Teaching Hospital, Beijing 100015, P.R. China
5. Department of Institute of Infectious Disease, Beijing Ditan Hospital, Capital Medical University, Beijing 100015, P.R. China