1. Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway
2. Norwegian Clinical Chemistry EQA Program, Bergen, Norway
3. Norwegian Quality Improvement of Primary Care Laboratories (NOKLUS), Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway
4. Department of Clinical Medicine, University of Bergen, Bergen, Norway
5. Department of Medicine, Haukeland University Hospital, Bergen, Norway
6. Laboratory of Clinical Biochemistry, Stavanger University Hospital, Stavanger, Norway