1. Department of Gastroenterology; Bethune International Peace Hospital; Shijiazhuang China
2. Department of Gastroenterology and Hepatology; Chinese PLA General Hospital; Beijing China
3. Department of Gastroenterology; Naval General Hospital; Beijing China
4. Department of Gastroenterology and Hepatology; Pakistan Institute of Medical Sciences; Islamabad Pakistan
5. Department of Epidemiology and Statistics; Hebei Medical University; Shijiazhuang China