[1] Capital Med Univ, Beijing Friendship Hosp, Natl Clin Res Ctr Digest Dis, Beijing 100050, Peoples R China
[2] Univ Cambridge, Sch Clin Med, Dept Publ Hlth & Primary Care, Primary Care Unit, Cambridge CB18RN, England
[3] Harvard Med Sch, Harvard Pilgrim Hlth Care Inst, Dept Populat Med, Boston, MA 02215 USA
[4] Peking Univ, Hlth Sci Ctr, Sch Publ Hlth, Dept Epidemiol & Biostat, Beijing 100191, Peoples R China
[5] Capital Med Univ, Beijing Friendship Hosp, Liver Res Ctr, 95 Yong An Rd, Beijing 100050, Peoples R China