The PubMed, MEDLINE, EMBASE, and Cochrane databases, as well as the conference proceed- ings from the annual meetings of the American Association for
the Study
of Liver Diseases,
the European Association for
the Study
of the Liver,
and the Asian Pacific Association for the Study of the Liver, were searched for articles published in English from January 1990 through May 2010, fulfilling the following criteria: (1) randomized, prospective observational, retrospective, or meta-analysis; (2) involv