1. Norwegian Organization for Quality Improvement of Laboratory Examinations (Noklus), Haraldsplass Deaconess Hospital , Bergen , Norway
2. Department of Medical Biochemistry and Pharmacology , Norwegian Porphyria Centre, Haukeland University Hospital , Bergen , Norway
3. Department of Global Public Health and Primary Care , University of Bergen , Bergen , Norway
4. Laboratory Medicine, IRCCS San Raffaele Scientific Institute , Milan , Italy
5. School of Science and Engineering, University of Dundee , Dundee , Scotland
6. Acibadem Mehmet Ali Aydınlar University, School of Medicine , Istanbul , Türkiye
7. Hospital Universitario La Paz, Quality Analytical Commission of Spanish Society of Clinical Chemistry (SEQC) , Madrid , Spain
8. Certe, Wilhelmina Ziekenhuis Assen , Assen , The Netherlands