Systematic review
A systematic review is a literature review focused on a research question that tries to identify, appraise, select and synthesize all high quality research evidence relevant to that question. Systematic reviews of high-quality randomized controlled trials are crucial to evidence-based medicine.[1] An understanding of systematic reviews and how to implement them in practice is becoming mandatory for all professionals involved in the delivery of health care. Besides health interventions, systematic reviews may concern clinical tests, public health interventions, adverse effects, and economic evaluations.[2]
Systematic reviews are not limited to medicine and are quite common in other sciences where data are collected, published in the literature, and an assessment of methodological quality for a precisely defined subject would be helpful.[3] Other fields where systematic reviews are used include psychology, nursing, public health, occupational therapy, speech therapy, physical therapy, educational research, sociology and business management.
Contents |
[edit] Characteristics
A systematic review aims to provide an exhaustive summary of literature relevant to a research question. The first step of a systematic review is a thorough search of the literature for relevant papers. The Methodology section of the review will list the databases and citation indexes searched, such as Web of Science, Embase, and PubMed, as well as any individual journals. Next, the titles and the abstracts of the identified articles are checked against pre-determined criteria for eligibility and relevance. This list will depend on the research problem. Each paper may be assigned an objective assessment of methodological quality using the Jadad scale or similar rating system.[4][5][6]
Systematic reviews often, but not always, use statistical techniques (meta-analysis) to combine results of the eligible studies, or at least use scoring of the levels of evidence depending on the methodology used. An additional rater may be consulted to resolve any scoring differences between raters. [7] Systematic review is often applied in the biomedical or healthcare context, but it can be applied in any field of research. Groups like the Campbell Collaboration are promoting the use of systematic reviews in policy-making beyond just healthcare.
A systematic review uses an objective and transparent approach for research synthesis, with the aim of minimizing bias. While many systematic reviews are based on an explicit quantitative meta-analysis of available data, there are also qualitative reviews which adhere to the standards for gathering, analyzing and reporting evidence. The EPPI-Centre has been influential in developing methods for combining both qualitative and quantitative research in systematic reviews.[8]
Recent developments in systematic reviews include realist reviews, developed by Ray Pawson and Trisha Greenhalgh, and the meta-narrative approach by Greenhalgh and colleagues.[9][10] These approaches try to overcome the problems of methodological and epistemological heterogeneity in the diverse literatures existing on some subjects. The CONSORT statement suggests a standardized way to report on parallel group randomized trials, and is now required for this kind of result by most medical journals.[11]
[edit] Cochrane Collaboration
Many healthcare journals now publish systematic reviews, but the best-known[citation needed] source is The Cochrane Collaboration, a group of over 28,000 specialists in health care who systematically review randomised trials of the effects of prevention, treatments and rehabilitation as well as health systems interventions. When appropriate, they also include the results of other types of research. Cochrane Reviews are published in The Cochrane Database of Systematic Reviews section of The Cochrane Library. The 2010 impact factor for The Cochrane Database of Systematic Reviews was 6.186, and it was ranked 10th in the “Medicine, General & Internal” category.[12]
The Cochrane Group provides a handbook for systematic reviewers of interventions which "provides guidance to authors for the preparation of Cochrane Intervention reviews."[13] The Cochrane Handbook outlines eight general steps for preparing a systematic review:[13]
- Defining the review question and developing criteria for including studies
- Searching for studies
- Selecting studies and collecting data
- Assessing risk of bias in included studies
- Analysing data and undertaking meta-analyses
- Addressing reporting biases
- Presenting results and "summary of findings" tables
- Interpreting results and drawing conclusions
[edit] Strengths and weaknesses
While systematic reviews are regarded as the strongest form of medical evidence, a review of 300 studies found that not all systematic reviews were equally reliable, and that their reporting could be improved by a universally agreed upon set of standards and guidelines.[14]
A further study by the same group found that of 100 systematic reviews monitored, 7% needed updating at the time of publication, another 4% within a year, and another 11% within 2 years; this figure was higher in rapidly-changing fields of medicine, especially cardiovascular medicine.[15] A 2003 study suggested that extending searches beyond major databases, perhaps into gray literature, would increase the effectiveness of reviews.[16]
Systematic reviews are increasingly appearing in other fields, such as international development research . Subsequently, a number of donors – most notably the UK Department for International Development (DFID) and AusAid – are focusing attention and resources on testing the appropriateness of systematic reviews in assessing the impacts of development and humanitarian interventions. [17]
[edit] See also
[edit] References
- ^ "What is EBM?". Centre for Evidence Based Medicine. 2009-11-20. http://www.cebm.net/index.aspx?o=1914. Retrieved 2011-06-17.
- ^ Systematic reviews: CRD's guidance for undertaking reviews in health care. York: University of York, Centre for Reviews and Dissemination, 2008. ISBN 9781900640473. Retrieved 2011-06-17.
- ^ Herman J. Ader; Gideon J. Mellenbergh; with contributions by David J. Hand (2008). Methodological quality (chapter 3) in Advising on Research Methods: A consultant's companion. Johannes van Kessel Publishing. ISBN 978-90-79418-02-2.
- ^ Herman J. Ader; Gideon J. Mellenbergh; with contributions by David J. Hand (2008). Methodological quality (chapter 3) in Advising on Research Methods: A consultant's companion. Johannes van Kessel Publishing. ISBN 978-90-79418-02-2.
- ^ Harris Cooper & Larry V. Hedges (Eds) (1994). The Handbook of Research Synthesis. Russel Sage Foundation. ISBN 0-87154-226-9.
- ^ Harris Cooper (1998). Synthesizing research: A guide for literature reviews (third ed.). Sage Publications.
- ^ Herman J. Ader; Gideon J. Mellenbergh; with contributions by David J. Hand (2008). Methodological quality (chapter 3) in Advising on Research Methods: A consultant's companion. Johannes van Kessel Publishing. ISBN 978-90-79418-02-2.
- ^ Thomas J, Harden A, Oakley A, Oliver S, Sutcliffe K, Rees R, Brunton G, Kavanagh J (2004). Integrating qualitative research with trials in systematic reviews. British Medical Journal 328:1010-1012.
- ^ Fraser MacFarlane; Olivia Kyriakidou; Bate, Paul; Richard Peacock; Greenhalgh, Trisha (2005). Diffusion of Innovations in Health Service Organisations: A Systematic Literature (Studies in Urban and Social Change). Blackwell Publishing Professional. ISBN 0-7279-1869-9.
- ^ Greenhalgh T, Potts HWW, Wong G, Bark P, Swinglehurst D (2009). Tensions and paradoxes in electronic patient record research: A systematic literature review using the meta-narrative method. Milbank Q 2009;87:729–88. (alternate full text)
- ^ Herman J. Ader; Gideon J. Mellenbergh; with contributions by David J. Hand (2008). Methodological quality (chapter 3) in Advising on Research Methods: A consultant's companion. Johannes van Kessel Publishing. ISBN 978-90-79418-02-2.
- ^ The Cochrane Library. 2010 impact factor. Cochrane Database of Systematic Reviews (CDSR). Frequently asked questions. Retrieved 2011-07-01.
- ^ a b Higgins JPT, Green S (editors). Cochrane handbook for systematic reviews of interventions, version 5.1.0 (updated March 2011). The Cochrane Collaboration, 2011. Retrieved 2011-06-17.
- ^ Moher D, Tetzlaff J, Tricco AC, Sampson M, Altman DG (2007). "Epidemiology and reporting characteristics of systematic reviews". PLoS Med. 4 (3): e78. doi:10.1371/journal.pmed.0040078. PMC 1831728. PMID 17388659. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1831728.
- ^ Shojania KG, Sampson M, Ansari MT, Ji J, Doucette S, Moher D (2007). "How quickly do systematic reviews go out of date? A survival analysis". Ann. Intern. Med. 147 (4): 224–33. PMID 17638714.
- ^ Savoie I, Helmer D, Green CJ, Kazanjian A (2003). "Beyond Medline: reducing bias through extended systematic review search". Int J Technol Assess Health Care 19 (1): 168–78. doi:10.1017/S0266462303000163. PMID 12701949.
- ^ Jessica Hagen-Zanker, Maren Duvendack, Richard Mallett and Rachel Slater with Samuel Carpenter and Mathieu Tromme. [Making systematic reviews work for international development research "Making systematic reviews work for international development research"]. Making systematic reviews work for international development research. Retrieved 19/01/2012.
[edit] External links
- Centre for Reviews and Dissemination, University of York.
- Cochrane Collaboration
- Evidence for Policy and Practice Information and Co-ordinating Centre (EPPI-Centre), University of London.
- MeSH: Review Literature - articles about the review process
- MeSH: Review [Publication Type] - limit search results to reviews
- PubMed search: "Review Literature"[MAJR]
- MIX 2.0 Software for professional meta-analysis in Excel.
- Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement, “an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses.”
