1. Department of Otorhinolaryngology-Head and Neck Surgery; Maastricht University Medical Center; Maastricht the Netherlands
2. Department of Methodology and Statistics; CAPHRI School for Public Health and Primary Care, Maastricht University; Maastricht the Netherlands
3. Department of Clinical Sciences; Institute of Tropical Medicine; Antwerp Belgium
4. Centre for Gastrointestinal Sciences; Institute of Inflammation and Repair, University of Manchester, Manchester Academic Health Sciences Centre, Salford Royal Hospital; Salford United Kingdom