What is a systematic review?
What's the difference between a 'systematic review' and a literature (or 'narrative') review?
Systematic reviews are characterised by:
- a clear, unambiguous research question
- a comprehensive search to identify all potentially relevant studies
- an explicit, reproducible and uniformly applied criteria for the inclusion/exclusion of studies
- a rigorous appraisal of the quality of individual studies, and
- a systematic synthesis of the results of included studies¹.
Other types of review are not required to follow this rigorous, transparent process. They can therefore be prone to bias in terms of how the author searches for studies and then selects, evaluates, and discusses them. Non systematic reviews provide no means to evaluate the completeness of the review or the author's agenda.
Cochrane Consumers and Communication Group video on why systematic reviews are important and how they are done.
Some useful pre-readings:
- Uman LS. Systematic reviews and meta-analyses. J Can Acad Child Adolesc Psychiatry. 2011 Feb; 20(1): 57–59.
- Petticrew M. Systematic reviews from astronomy to zoology: myths and misconceptions. BMJ. 2001 Jan; 322(7278): 98-101.
What's the difference between a systematic review and a meta-analysis?
'Meta-analysis' refers to the statistical technique often used by quantitative systematic reviews to integrate the results of included studies. This increases the power and precision of estimates of treatment effect or exposure risk. Not all systematic reviews include a meta-analysis and not all meta-analyses are undertaken "systematically"²
2. Cochrane Collaboration n.d., Glossary: Cochrane Community, accessed 20 Feb 2015, <http://community.cochrane.org/glossary/5#letterm>
In this video, Prof. Aaron Carroll explains meta-analysis using the nutrient content of organic food as an example.
Why are systematic reviews important?
Systematic reviews condense research evidence from multiple primary studies using a process designed to minimise the risk of reporting conclusions in a biased way. They therefore provide us with a far more comprehensive and trustworthy picture of the topic of interest than can be gained from individual pieces of research.
Systematic review and evidence-based medicine
In this video, Prof. Aaron Carroll gives an interesting overview of systematic reviews and their importance to evidence based medicine.
Systematic reviews may be published in the peer-reviewed journal literature. You can find these reviews using databases and restricting your search to publication type 'systematic review'.
Systematic reviews are also produced by government, NGOs, agencies and academic institutions and made available on websites. These reviews are an example of 'unpublished' (or 'grey') research. To find these reviews, you need to:
- check the websites of relevant organisations
or, using Google Advanced Search, enter search terms for your topic in the top search box ('all these terms') as well as the phrase 'systematic review'.
Major producers of systematic reviews
The Cochrane Collaboration is a global independent network of health practitioners, researchers, and patient advocates producing systematic reviews of primary research in human health care and health policy. Cochrane reviews are internationally recognised as the highest standard in evidence-based health care.
Cochrane reviews are published online in The Cochrane Library.
The Joanna Briggs Institute (JBI) is the international not-for-profit, research and development arm of the School of Translational Science based within the Faculty of Health Sciences at the University of Adelaide, South Australia. JBI collaborates internationally with over 70 entities across the world in producing systematic reviews. JBI reviews are published in the subscription journal JBI Database of Systematic Reviews and Implementation Reports.
EPPI-Centre is part of the Social Science Research Unit at the Institute of Education, University of London. It conducts systematic reviews across a range of topics and works with a large number of funders.
Major areas include:
- Education and social policy
- Health promotion and public health
- International health systems and development
- Participative research and policy.
Full reviews can be found in the Centre’s online Evidence Library.
Find PubMed articles about systematic reviews
Click on a link below to launch a real-time PubMed search for literature on:
Tools for producing systematic reviews
Manuals for conducting systematic reviews
Video tutorial series
An excellent series of video tutorials from Yale University's Harvey Cushing/John Hay Whitney Medical Library). These cover topics such as: how to do a systematic review; building search strategies; finding grey literature; and using filters to restrict to specific study designs.