1 Center for Crohn's and Colitis, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; Center for Clinical Epidemiology, Odense University Hospital, and Research Unit of Clinical Epidemiology, University of Southern Denmark, Odense, Denmark. Electronic address: sfriedman1@partners.org.
2 Center for Crohn's and Colitis, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA; Center for Clinical Epidemiology, Odense University Hospital, and Research Unit of Clinical Epidemiology, University of Southern Denmark, Odense, Denmark.