1. Section of Gastroenterology & Ege Reflux Study Group, Ege University, Izmir, Turkey
2. Central Research Institute of Gastroenterology, Moscow, Russia
3. Department of Biostatistics & Ege Reflux Study Group, Ege University, Izmir, Turkey
4. Department of Pathology of Upper Digestive Tract, Moscow Clinical and Research Center, Moscow, Russia