1. Department of Gastroenterology, Peking University Third Hospital, Beijing, China
2. Beijing Key Laboratory for Helicobacter Pylori Infection and Upper Gastrointestinal Diseases (BZ0371), Beijing, China
3. Department of Microbiology and Infectious Disease Center, School of Basic Medical Sciences, Peking University Health Science Center, Beijing, China
4. Department of Laboratory Medicine, Beijing Tongren Hospital, Capital Medical University, Beijing, China
5. Research Center of Clinical Epidemiology, Peking University Third Hospital, Beijing, P.R. China