1London Region Breast Screening Programme, Quality Assurance Reference Centre, St Bartholomew's Hospital, London, UK
2Department of Epidemiology and Biostatistics, EUREF Office 451, Radboud University Medical Centre Nijmegen, Nijmegen, The Netherlands
3Centre fribourgeois de dépistage du cancer du sein, Fribourg, Switzerland
4Cancer Screening Unit, Karolinska University Hospital, Stockholm, Sweden
5National Expert and Training Centre for Breast, Cancer Screening, EUREF Office 451, Radboud University Medical Centre Nijmegen, Nijmegen, The Netherlands
6Screening Quality Control Group, European Cancer Network Coordination Office, International Agency for Research on Cancer, Lyon cedex, France