1. NKC Institute of Gastroenterology and Hepatology, Faculty of Medicine, Prince of Songkla University, Songkhla, Thailand
2. Division of Gastroenterology, Department of Medicine, King Chulalongkorn Memorial Hospital, The Thai Red Cross Society, Bangkok, Thailand
3. Center of Excellence in Neurogastroenterology and Motility, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand