[1] Kaiser Permanente No Calif, Dept Gastroenterol, Santa Clara, CA USA
[2] Kaiser Permanente No Calif, Div Res, Oakland, CA 94612 USA
[3] Univ Calif San Francisco, Div Gastroenterol, Dept Internal Med, San Francisco, CA 94143 USA
[4] Univ Penn, Dept Med Biostat & Epidemiol, Philadelphia, PA 19104 USA
[5] Univ Penn, Ctr Clin Epidemiol & Biostat, Philadelphia, PA 19104 USA
[6] Ctr Dis Control & Prevent, Div Adult & Community Hlth, Natl Ctr Chron Dis Prevent & Hlth Promot, Atlanta, GA USA
[7] Johns Hopkins Univ, Div Gastroenterol & Hepatol, Baltimore, MD USA
[8] Kaiser Permanente, Div Pediat Gastroenterol, Santa Clara, CA USA