Sacramento Veterans Affairs Medical Center, VA Northern California Health Care System, Division of Gastroenterology, Mather, California, USA; University of California Davis School of Medicine, Sacramento, California, USA. Clinical and Translational Science Center, Department of Public Health Sciences, Division of Biostatistics, University of California Davis, Sacramento, California, USA. Sepulveda Ambulatory Care Center, VA Greater Los Angeles Healthcare System, Division of Gastroenterology, North Hills, California, USA; David Geffen School of Medicine at UCLA, Los Angeles, California, USA.