[1] Natl Hlth Insurance Serv Ilsan Hosp, Dept Internal Med, Div Gastroenterol, Goyang, South Korea
[2] Natl Hlth Insurance Serv Ilsan Hosp, Dept Policy Res Affairs, Goyang, South Korea
[3] Natl Hlth Insurance Serv, Hlth Insurance Res Inst, Wonju, South Korea
[4] Natl Hlth Insurance Serv Ilsan Hosp, Dept Internal Med, Div Gastroenterol, 100 Ilsanro, Goyang Si 10444, Gyeonggi Do, South Korea