[1] Johns Hopkins Univ, Sch Med, Div Gastroenterol & Hepatol, Baltimore, MD 21205 USA
[2] Johns Hopkins Univ, Sinai Hosp Program Internal Med, Baltimore, MD 21205 USA
[3] Johns Hopkins Univ, Sch Med, Dept Epidemiol, Baltimore, MD 21205 USA
[4] Univ Texas SW Med Sch, VA N Texas Healthcare Syst, Dept Med, Div Gastroenterol & Hepatol, Dallas, TX USA
[5] Univ Penn Hlth Syst, Div Gastroenterol, Philadelphia, PA USA