Affiliation: | 1. Department of Internal Medicine and Clinical Sciences, University of Texas Southwestern Medical Center, Dallas, Texas;3. VA San Diego Healthcare System and Department of Internal Medicine, Division of Gastroenterology, University of California San Diego, La Jolla, California;4. Department of Internal Medicine, University of California San Francisco, San Francisco, California;6. Group Health Research Institute, Seattle, Washington;5. Division of Research, Kaiser Permanente Northern California, Oakland, California |