1. Department of Gastroenterology, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China
2. Medical Research Center, Peking Union Medical College Hospital, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China
3. State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Beijing 100730, China
4. Department of Epidemiology and Biostatistics, School of Population Medicine and Public Health, Peking Union Medical College, Chinese Academy and Medical Sciences, Beijing 100730, China
5. Department of Family Medicine and Primary Care, JC School of Public Health and Primary Care, Faculty of Medicine, Chinese University of Hong Kong, Hong Kong 999077, China
6. Department of Health Research Methods, Evidence and Impact, McMaster University, Hamilton,Ontario L8S4L8, Canada
7. Centre for Health Economics and Policy Analysis, McMaster University, Hamilton, Ontario L8S4L8, Canada
8. Clinical Epidemiology Unit, International Clinical Epidemiology Network, Beijing 100730, China.