1. Referral Center for Pediatric Gastroenterology and Nutrition, Children's Hospital Zagreb, Klaićeva 16, Zagreb, Croatia;
2. 2nd Department of Pediatrics, Medical University of Warsaw, Warsaw, Poland;
3. Department for Environmental and Occupational Health, “Andrija Štampar” School of Public Health, Rockefellerova 4, Zagreb, Croatia; and
4. Division of Gastroenterology and Hepatology, University Hospital Center Zagreb, Kispaticeva 12, Zagreb, Croatia