1. Colorectal Cancer Screening Programme Coordination Center, Bilbao, Spain
2. BioCruces Health Research Institute, Barakaldo, Spain
3. Basurto-Bilbao Health Organization, Osakidetza-Basque Health Service, Bilbao, Spain
4. Araba Health Organization, Osakidetza-Basque Health Service, Vitoria, Spain
5. Hospital Universitario Donostia/Instituto Biodonostia, Red de Investigación en Servicios de Salud en Enfermedades Crónicas (REDISSEC), San Sebastián, Spain
6. Gastroenterology Department, Instituto Biodonostia, University of Basque Country (UPV/EHU), Centro de Investigación Biomédica en Red de Enfermedades Hepaticas y Digestivas (CIBERehd), San Sebastián, Spain