[1] Mayo Clin, Coll Med, Dept Internal Med, Jacksonville, FL 32224 USA
[2] Mayo Clin, Coll Med, Div Gastroenterol & Hepatol, Jacksonville, FL 32224 USA
[3] Peking Univ, Peoples Hosp, Div Gastroenterol & Hepatol, Beijing 100871, Peoples R China
[4] Mayo Clin, Coll Med, Dept Hlth Sci Res, Div Biostat, Rochester, MN USA