1. Department of Laboratory Medicine , National University Hospital , Singapore , Singapore
2. Norwegian Organization for Quality Improvement of Laboratory Examinations (NOKLUS), Haraldsplass Deaconess Hospital , Bergen , Norway
3. Department of Medical Biochemistry and Pharmacology , Norwegian Porphyria Centre, Haukeland University Hospital , Bergen , Norway
4. Institute of Public Health and Primary Health Care, University of Bergen , Bergen , Norway
5. Department of Chemical Pathology , New South Wales Health Pathology, Prince of Wales Hospital , Sydney , Australia