[1] Shandong First Med Univ, Dept Gastroenterol, Affiliated Hosp 2, Tai An, Shandong, Peoples R China
[2] Capital Med Univ, Beijing Friendship Hosp, Dept Gastroenterol, 95 Yongan Rd, Beijing 100050, Peoples R China
[3] Beijing Digest Dis Ctr, Beijing Key Lab Precancerous Lesion Digest Dis, Natl Clin Res Ctr Digest Dis, Beijing, Peoples R China