T HE INTERNET HAS BECOME AN IMportant mass medium for consumers seeking health information and health care services online.1 A recent concern and public health issue has been the quality of health information on the World Wide Web. However, the scale of the problem and the "epidemiology" (distribution and determinants) of poor health information on the Web are still unclear, as is their impact on public health and the question of whether poor health information on the Web is a problem at all. 2 Many studies have been conducted to describe, critically appraise, and analyze consumer health information on the Web. These typically report proportions of inaccurate or imperfect information as estimates of the prevalence of flawed information or the risk of encountering misinformation on the Web.However, to date no systematic and comprehensive synthesis of the methodology and evidence has been attempted. Two previous systematic reviews focused on compiling quality criteria and rating instruments, but did not synthesize evaluation results. Jadad and Gagliari 3 reviewed nonresearch-based rating systems (eg, criAuthor Affiliations: Unit for Cybermedicine and EHealth, Department of Clinical Social Medicine, University of Heidelberg, Heidelberg, Germany (Dr Eysenbach); Health Services Research Unit, London School of Hygiene and Tropical Medicine, London, England (Dr Powell); Department of Medical Epidemiology, Biometry and Informatics, University of Halle-Wittenberg, Halle/Saale, Germany (Dr Kuss); and Global Health Network Group, Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pa (Ms Sa). Dr Eysenbach is now with the Centre for Global eHealth Innovation, Toronto General Hospital, Toronto, Ontario. Corresponding Author and Reprints: Gunther Eysenbach, MD, Centre for Global eHealth Innovation, Toronto General Hospital, 190 Elizabeth St, Toronto, Ontario,.
ContextThe quality of consumer health information on the World Wide Web is an important issue for medicine, but to date no systematic and comprehensive synthesis of the methods and evidence has been performed.
ObjectivesTo establish a methodological framework on how quality on the Web is evaluated in practice, to determine the heterogeneity of the results and conclusions, and to compare the methodological rigor of these studies, to determine to what extent the conclusions depend on the methodology used, and to suggest future directions for research. . We also conducted hand searches, general Internet searches, and a personal bibliographic database search.
Data Sources We searched MEDLINE and PREMEDLINE (1966 throughSeptem
Study SelectionWe included published and unpublished empirical studies in any language in which investigators searched the Web systematically for specific health information, evaluated the quality of Web sites or pages, and reported quantitative results. We screened 7830 citations and retrieved 170 potentially eligible full articles. A total of 79 distinct studies met the inclusion criteria, evaluating 5941 health Web sites and 1329 Web...