Defining Systematic Reviews

Definitions of systematic reviews vary but most would aim to gather all available literature to answer a research question by:

• a clearly stated set of objectives with pre-defined eligibility criteria for studies;
• an explicit, reproducible methodology;
• a systematic search that attempts to identify all studies (published and sometimes unpublished) that would meet the eligibility criteria;
• an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and
• a systematic presentation, and synthesis, of the characteristics and findings of the included studies.

Types of Systematic Reviews

There are different types of Systematic Reviews. It is important to know what type you are doing in order that you can carry out all the steps of the processes correctly. Systematic reviews come in many shapes and sizes and vary between subjects.  Complex questions can involve large teams of researchers and can take months to complete. Smaller reviews can involve one or two people.

Ideally the screening of results should always be carried out by two people independently. Resources and time will influence what level of review you can complete. It is vital that you discuss with your supervisor exactly what they expect you to do. Conducting a systematic review, although it does involve a series of steps, is not a linear process.  You may need to revisit some of the steps more than once.

For more information, on different types of reviews take a look at the Definitions of Reviews document below.

Decision Tree

Use our Decision Tree to decide which type of Systematic Review you are doing.

If you would answer Yes to any of the following questions then it may be that you are doing a systematic literature review rather than a systematic review.

1. Are you expected to include only published material (excluding conference papers, Randomised Control Trials (RCTs), dissertations, theses)?
2. Are you being led to search only in a restricted number of databases?
3. Have you been told to include only a specific number of results?
4. Have you been advised to limit by date or language to restrict the numbers of results?

If Yes is the answer, then this guide will still be of use to you, but you may not have to follow all the steps in full. Always check with a supervisor and discuss if you are unsure.

If you plan to carry out a scoping or systematic review you will be expected to carry out the steps below. 

All the steps are required for a Systematic Review but only those lines with a * and highlighted in bold for a Scoping Review:

1. formulate/ define your research question 
2. justify the need for a Systematic Review 
3. produce a protocol and define the parameters 
4. *identify appropriate bibliographic sources to search 
5. *design search strategy and undertake systematic literature search
6. *ensure that any known relevant papers appear in the search results
7. *manage search results 
8. screen search results 
9. perform quality assessment on included studies, including risk of bias 
10. data extraction from included studies 
11. assess heterogeneity of studies 
12. perform data synthesis – meta-analysis/narrative synthesis - and interpret findings
13. write up findings with recommendations in final report
14. undertake dissemination

Library staff are available to offer support to postgraduate students and research staff for steps 4-7 of this Systematic Reviews process.