1. Alimentary Tract Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
2. Liver and Pancreatobiliary Diseases Research Center, Digestive Diseases Research Institute, Tehran University of Medical Sciences, Tehran, Iran
3. Department of Bio-statistics and Epidemiology, Faculty of Public Health, Tehran University of Medical Sciences, Tehran, Iran
4. Department of Biostatistics and Epidemiology, School of Public Health, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
5. Faculty of Medicine, Behbahan University of Medical Sciences, Behbahan, Iran
6. Faculty of Medicine, Dezful University of Medical Sciences, Dezful, Iran
7. Department of Clinical Immunology and Allergy, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
8. Shoushtar School of Medical Sciences and Health Services, Shoushtar, Iran
9. Abadan Faculty of Medical Sciences, Abadan, Iran
10. Physiology Research Center, School of Public Health, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
11. Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, Maryland, United States
12. Alimentary Tract Research Center, School of Medicine, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran