1Section for Colorectal Cancer Screening, Cancer Registry of Norway, P.O. Box 5313 Majorstuen, 0304 Oslo, Norway
2Department of Research and Development, Telemark Hospital Trust, Ulefossvegen 55, 3710 Skien, Norway
3Institute of Clinical Medicine, University of Oslo, P.O. Box 1171 Blindern, 0318 Oslo, Norway
4Department of Medicine, Sørlandet Hospital, P.O. Box 416 Lundsiden, 4604 Kristiansand, Norway
5Institute for Health and Society, University of Oslo, P.O. Box 1130 Blindern, 0318 Oslo, Norway
6Department of Research, Cancer Registry of Norway, P.O. box 5313 Majorstuen, 0304 Oslo, Norway