1. Department of Otolaryngology, Head and Neck Surgery, Sahlgrenska University Hospital, Göteborg, Sweden
2. SPRI (Swedish Institute for Health Services Development), Stockholm, Sweden
3. *Department of Otolaryngology, Head and Neck Surgery, Sahlgrenska University Hospital, Göteborg, Sweden; and Sheffield Teaching Hospitals, Department of Otorhinolaryngology, Head and Neck Surgery, Royal Hallamshire Hospital, Sheffield, UK