The Role of Evidence Synthesis and Meta-Analysis in Health care

Health care professionals, policy makers, researchers and consumers of the health services have roles and responsibilities in making decisions regarding alternative options, such as choosing from a wide choice of antidepressants for the cure of acute depression. Synthesis of the results from relevant studies informs their choices. The systematic reviews toolkit, and its quantitative component, meta-analysis, consist a useful roadmap towards evidence-based medicine by summarizing large amounts of information concerning the relative effectiveness of health care interventions in an objective and transparent way. Systematic reviews can also play an important role in prioritizing research by identify gaps and flagging out conceptual or methodological deficiencies in the existing evidence and inform the future research agenda. Many organizations, including World Health Organisation (WHO) and several governmental agencies from many countries around the world have recognized the need to ensure that the best available evidence informs guidelines for clinical practice and this typically involves meta-analyses. Systematic reviews also influence the policy making in an indirect way more than individual studies do, as they often feature in the news media; see for example the case of environmental tobacco (Kennedy & Bero, 1999). It has been shown that meta-analysis is the most highly cited and therefore influential publication in health research (Patsopoulos et al., 2005).

It is important that such influential resources as meta-analysis be grounded in sound methodology. There is a vast literature on how to conduct a review and synthesize its results; it is a process that requires input from many disciplines and typically involves medical professionals, librarians, policy makers, epidemiologists and statisticians.

The methodological foundation of meta-analysis has been fostered largely within the Cochrane Collaboration ( The Cochrane Collaboration is an international non-profit organization undertaking systematic reviews of the effects of health care interventions. Nowadays it involves a few thousands of reviewers and methodologists and is responsible for the publication and update of over 3000 systematic reviews, which reach specialists and the general public through a comprehensive strategy of dissemination (such as press releases, online podcasts etc, Since its foundation about twenty years ago the Cochrane Collaboration has been playing a pioneering role in promoting evidence-based clinical practice at large, providing training and support to the reviewers and undertaking methodological research in order to improve the quality of the output. In the recent years, closed links are being established between the Cochrane Collaboration and WHO particularly in developing clinical and public health guidelines.


Kennedy, G. E. Bero, L. A. (1999). Print media coverage of research on passive smoking. Tob. Control 8, 254-260

Patsopoulos, N. A., Analatos, A. A., Ioannidis, J. P. (2005). Relative citation impact of various study designs in the health sciences. JAMA 293, 2362-2366

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