Julian P.T. Higgins, George Davey Smith, Douglas G. Altman, Matthias Egger
The principles and steps of systematic reviews are similar to any other research undertaking: formulation of the problem to be addressed, collection and analysis of the data, and interpretation of the results. A study protocol should be written, which states objectives and eligibility criteria, describes how studies will be identified and selected, explains how any assessment of methodological quality or risk of bias will be undertaken, and provides details of any planned synthesis methods. The results from eligible studies are expressed in a standardized format and are often displayed graphically in forest plots with confidence intervals. Heterogeneity between study results and possible biases may be explored graphically in a forest, funnel, and other plots, and in statistical analyses. If a meta-analysis is deemed appropriate, a typical effect is estimated by combining the data. Most meta-analysis methods follow either fixed-effect(s) or random-effects approaches, which differ in the way they treat between-study heterogeneity. Meta-analyses generally use relative effect measures, while absolute measures are used when applying the findings to clinical or public health situations.
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Julian P.T. Higgins
Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
National Institute of Health Research, Applied Research Collaboration West, University Hospital Bristol and Weston NHS Foundation Trust, Bristol, UK
George Davey Smith
Medical Research Council Integrative Epidemiology Unit, Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK
Douglas G. Altman
Centre for Statistics in Medicine, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, UK
Institute of Social and Preventive Medicine, University of Bern, Bern, Switzerland
Centre for Infectious Diseases, Epidemiology and Research, University of Cape Town, South Africa
How to cite this chapter?
For the printed version of the book
Higgins, J.P.T., Davey Smith, G., Altman, D.G. and Egger, M. (2022). Chapter 2. Principles of systematic reviewing. In: Systematic Reviews in Health Research: Meta-analysis in Context (eds M. Egger, J.P.T. Higgins and G. Davey Smith), pp 17-35. Hoboken, NJ : Wiley.
For the electronic version of the book
Higgins, J.P.T., Davey Smith, G., Altman, D.G. and Egger, M. (2022). Chapter 2. Principles of systematic reviewing. In: Systematic Reviews in Health Research: Meta-analysis in Context (eds M. Egger, J.P.T. Higgins and G. Davey Smith). https://doi.org/10.1002/9781119099369.ch2