1. Department of Gastroenterology, The Second Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 455000, China
2. Department of Pathology, The Second Affiliated Hospital of Zhengzhou University, Zhengzhou, Henan 455000, China
3. Institute of Clinical Medicine, Norwegian University of Science and Technology, 7489 Trondheim, Norway
4. Institute of Health, Nord-Trøndelag University College, 7600 Levanger, Norway