1. Medical College of Qingdao University, Qingdao, Shandong 266071, P.R. China
2. Central Laboratories, Qingdao Municipal Hospital, Qingdao, Shandong 266071, P.R. China
3. Department of Gastroenterology, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China
4. Department of Infectious Disease, Qingdao Municipal Hospital, Qingdao, Shandong 266011, P.R. China