1. Clinical Effectiveness Research Group Institute of Health and Society, University of Oslo Oslo Norway
2. Clinical Effectiveness Research Group Department of Transplantation Medicine, Oslo University Hospital Oslo Norway
3. Department of Pathology Oslo University Hospital Oslo Norway
4. Department of Medicine Nordland Hospital Bodø Bodø Norway
5. Department of Medicine Sørlandet Hospital Kristiansand Kristiansand Norway
6. Department of Medical Epidemiology and Biostatistics Karolinska Institute Stockholm Sweden
7. Department of Epidemiology Harvard T. H. Chan School of Public Health Boston Massachusetts USA