1. School of Medicine Cardiff University Cardiff UK
2. Division of Gastroenterology and Hepatology, Department of Internal Medicine University of Texas Medical Branch Galveston Texas USA
3. French Porphyria Reference Center (CRMR Porphyries France) University Paris Paris France
4. Department of Medical Biochemistry and Biophysics, Centre for inherited Metabolic Diseases, Porphyria Centre Sweden, Karolinska Institutet Karolinska University Hospital Stockholm Sweden
5. Department of Medical Biochemistry and Pharmacology, Norwegian Porphyria Centre Haukeland University Hospital Bergen Norway
6. Norwegian Organization for Quality Improvement of Laboratory Examinations (Noklus) Haraldsplass Deaconess Hospital Bergen Norway
7. Institute of Public Health and Primary Health Care University of Bergen Bergen Norway