[1] Showa Univ, Northern Yokohama Hosp, Digest Dis Ctr, 35-1 Tsuzuki, Yokohama, Kanagawa 2248503, Japan
[2] Showa Univ, Northern Yokohama Hosp, Dept Diagnost Pathol, Yokohama, Kanagawa, Japan
[3] Tokyo Med & Dent Univ, Med Hosp, Dept Endoscopy, Tokyo, Japan
[4] Univ Oslo, Clin Effectiveness Res Grp, Oslo, Norway