[1] Boston Univ, Med Ctr, Internal Med, Boston, MA 02215 USA
[2] Boston Univ, Med Ctr, Gastroenterol, Boston, MA 02215 USA
[3] Univ Iowa, Biostat & Res Design, Inst Clin & Translat Sci, Iowa City, IA 52242 USA
[4] Univ Iowa, Sch Med, Iowa City, IA 52242 USA
[5] Univ Iowa Hosp & Clin, Iowa City, IA 52242 USA