1. Department of Clinical Biochemistry and Clinical Genetics, Odense University Hospital, DK-5000 Odense C, Denmark and The Danish Centre of Porphyria;
2. Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, V6T 1W5 Canada;
3. Division of Clinical Chemistry, Vancouver Hospital and Health Sciences Centre, Vancouver, British Columbia, V5Z 1M9 Canada