1. Department of Pulmonary Medicine, Medisch Spectrum Twente, Enschede, The Netherlands
2. Department of gastroenterology, Tjongerschans, Heerenveen, The Netherlands
3. Department of Research Methodology, Measurement, and Data Analysis, University of Twente, Enschede, The Netherlands
4. Medical School Twente, Medisch Spectrum Twente, Enschede, The Netherlands
5. Department of Pulmonary Medicine, and Groningen Research Institute for Asthma and COPD (GRIAC), University of Groningen, University Medical Centre Groningen, Groningen, The Netherlands