1. Department of Gastroenterology, The Affiliated Hospital of Qingdao University, Qingdao, China
2. School of Mathematics, Shandong University, Jinan, China
3. Department of General Practice, The Third People's Hospital of Chengdu, Chengdu, China
4. Division of Gastroenterology, Liyuan Hospital, Tongji Medical College, Huazhong University of Science & Technology, Wuhan, 430077, China