1. Norwegian Organization for Quality Improvement of Laboratory Examinations (Noklus) , Haraldsplass Deaconess Hospital , Bergen , Norway
2. Norwegian Porphyria Centre, Department of Medical Biochemistry and Pharmacology , Haukeland University Hospital , Bergen , Norway
3. Department of Global Public Health and Primary Care , University of Bergen , Bergen , Norway
4. Institute of Medical Chemistry and Laboratory Medicine, 1st Faculty of Medicine , Charles University and General University Hospital , Prague , Czech Republic
5. Department of Laboratory Medicine, Ludwik Rydygier Collegium Medicum in Bydgoszcz , Nicolaus Copernicus University in Torun , Torun , Poland