[1] Massachusetts Gen Hosp, Gastrointestinal Unit, Boston, MA 02114 USA
[2] Massachusetts Gen Hosp, Dept Pathol, Boston, MA 02114 USA
[3] Massachusetts Gen Hosp, MGH Biostat Ctr, Boston, MA 02114 USA
[4] Harvard Univ, Sch Med, Boston, MA USA
[5] Bon Secours Richmond Hlth Syst, Dept Internal Med, Richmond, VA USA