A
systematic review is a
literature reviewA literature review is a body of text that aims to review the critical points of current knowledge and or methodological approaches on a particular topic...
focused on a single 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 trialA randomized controlled trial is a type of scientific experiment most commonly used in testing the efficacy or effectiveness of healthcare services or health technologies . RCTs are also employed in other research areas, such as judicial, educational, and social research...
s are crucial to
evidence-based medicineEvidence-based medicine aims to apply the best available evidence gained from the scientific method to medical decision making. It seeks to assess the quality of evidence of the risks and benefits of treatments ....
. An understanding of systematic reviews and how to implement them in practice is becoming mandatory for all professionals involved in the delivery of
health careHealth care , is the treatment and management of illness, and the preservation of health through services offered by the medical, dental, complementary and alternative medicine, pharmaceutical, clinical laboratory sciences , nursing, and allied health professions...
.
A systematic review is a summary of research that uses explicit methods to perform a thorough literature search and critical appraisal of individual studies to identify the valid and applicable evidence.
A
systematic review is a
literature reviewA literature review is a body of text that aims to review the critical points of current knowledge and or methodological approaches on a particular topic...
focused on a single 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 trialA randomized controlled trial is a type of scientific experiment most commonly used in testing the efficacy or effectiveness of healthcare services or health technologies . RCTs are also employed in other research areas, such as judicial, educational, and social research...
s are crucial to
evidence-based medicineEvidence-based medicine aims to apply the best available evidence gained from the scientific method to medical decision making. It seeks to assess the quality of evidence of the risks and benefits of treatments ....
. An understanding of systematic reviews and how to implement them in practice is becoming mandatory for all professionals involved in the delivery of
health careHealth care , is the treatment and management of illness, and the preservation of health through services offered by the medical, dental, complementary and alternative medicine, pharmaceutical, clinical laboratory sciences , nursing, and allied health professions...
.
Characteristics
A systematic review is a summary of research that uses explicit methods to perform a thorough literature search and critical appraisal of individual studies to identify the valid and applicable evidence. It is often applied in the
biomedicalBiomedical research , in general simply known as medical research, is the basic research, applied research, or translational research conducted to aid and support the body of knowledge in the field of medicine...
or healthcare context, but systematic reviews can be applied in any field of research and groups like the
Campbell CollaborationThe Campbell Collaboration is a non-profit organization that applies a rigorous, systematic process to review the effects of interventions in the social, behavioral and educational arenas, in order to provide evidence-based information in the shape of systematic reviews.The organization was...
are promoting their use in policy-making beyond just healthcare. It often, but not always, uses statistical techniques (
meta-analysisIn statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. This is normally done by identification of a common measure of effect size, which is modelled using a form of meta-regression...
) to combine these valid studies, or at least uses grading of the levels of evidence depending on the methodology used.
A systematic review uses an objective and transparent approach for research synthesis, with the aim of minimising bias.
While many systematic reviews are based on an explicit
quantitativeQuantitative research is the systematic scientific investigation of quantitative properties and phenomena and their relationships. The objective of quantitative research is to develop and employ mathematical models, theories and/or hypotheses pertaining to natural phenomena...
meta-analysisIn statistics, a meta-analysis combines the results of several studies that address a set of related research hypotheses. This is normally done by identification of a common measure of effect size, which is modelled using a form of meta-regression...
of available data, there are also
qualitativeQualitative research is a field of inquiry applicable to many disciplines and subject matters. Qualitative researchers aim to gather an in-depth understanding of human behavior and the reasons that govern such behavior. The qualitative method investigates the why and how of decision making, not...
reviews which adhere to the standards for gathering, analyzing and reporting evidence. The
EPPI-CentreThe Evidence for Policy and Practice Information and Co-ordinating Centre is part of the Social Science Research Unit at the Institute of Education, University of London...
have been influential in developing methods for combining both qualitative and quantitative research in systematic reviews.
Recent developments in systematic reviews include realist reviews, developed by Ray Pawson and Trisha Greenhalgh, and the meta-narrative approach. These approaches try to overcome the problems of methodological and
epistemologicalEpistemology or theory of knowledge is the branch of philosophy concerned with the nature and scope of knowledge...
heterogeneity in the diverse literatures existing on some subjects.
Cochrane Collaboration
Many healthcare
journalsIn academic publishing, a scientific journal is a periodical publication intended to further the progress of science, usually by reporting new research. There are thousands of scientific journals in publication, and many more have been published at various points in the past...
now publish systematic reviews, but the best-known source is The Cochrane Collaboration, a group of over 15,000 specialists in health care who systematically review randomised trials of the effects of treatments and, when appropriate, the results of other research. Cochrane reviews are published in
The Cochrane Database of Systematic Reviews section of The Cochrane Library, which to date (January 2009) contains 3,625 complete reviews and 1,921 protocols for additional reviews being conducted.
The Cochrane Group provides a
handbook for systematic reviewers of interventions, where they suggest that each systematic review should contain the following main sections:
- Background
- Objectives
- Methods of the review
- Results
- Conclusion and discussion
There are seven steps for preparing and maintaining a systematic review, as outlined in the
Cochrane Handbook:
- Formulating a problem
- Locating and selecting studies
- Critical appraisal of studies
- Collecting data
- Analyzing and presenting results
- Interpreting results
- Improving and updating reviews
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.
A further study by the same group found that of 100 guidelines reviewed, 4% required updating within a year, and 11% after 2 years; this figure was higher in rapidly-changing fields of medicine, especially cardiovascular medicine. 7% of systematic reviews needed updating at the time of publication. A 2003 study suggested that extending searches beyond major databases, perhaps into
gray literatureGrey literature is a term used variably by the intelligence community, librarians, and medical and research professionals to refer to a body of materials that cannot be found easily through conventional channels such as publishers, "but which is frequently original and usually recent" in the words...
, would increase the effectiveness of reviews.
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