1. a University of Leuven, Centre for Human Genetics, Biomedical Quality Assurance Research Unit, Leuven, Belgium;
2. b Department of Pathology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands;
3. d ESP KRAS Quality Assurance Workgroup, Brussels, Belgium
4. c University of Leuven, Department of Gastro-enterology, Leuven, Belgium;