1. Institute of Clinical Medicine, Faculty of Medicine University of Oslo Oslo Norway
2. Department of Otolaryngology, Head and Neck Surgery Oslo University Hospital Oslo Norway
3. Faculty of Chemistry, Biotechnology and Food Science Norwegian University of Life Sciences Ås Norway
4. Institute of Clinical Medicine, Campus Ahus University of Oslo Oslo Norway
5. Health Services Research Unit Akershus University Hospital Nordbyhagen Norway
6. Department of Otolaryngology, Head and Neck Surgery Akershus University Hospital Nordbyhagen Norway
7. Center for Clinical Research, Västerås Uppsala University Uppsala Sweden