[1] Mayo Clin, Div Allerg Dis, Rochester, MN 55905 USA
[2] Mayo Clin, Div Gastroenterol & Hepatol, Rochester, MN 55905 USA
[3] Mayo Clin, Div Biomed Stat & Informat, Rochester, MN 55905 USA
[4] Mayo Clin, Div Anat Pathol, Rochester, MN 55905 USA
[5] Univ Newcastle, Dept Internal Med, Fac Hlth, Newcastle, NSW 2300, Australia