1. Department of Otorhinolaryngology---Head and Neck Surgery, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
2. Skin and Allergy Hospital, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
3. Department of Otorhinolaryngology, Päijät-Häme Central Hospital, Lahti, Finland
4. Department of Otorhinolaryngology, University of Tampere, Faculty of Medicine and Health Technology and Tampere University Hospital, Tampere, Finland
5. Haartman Institute, University of Helsinki, Helsinki, Finland