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Systematic Reviews

Systematic Reviews

A systematic review aims to provide an unbiased answer to a research question with -
•    Clear objectives – and defined criteria for studies to be included.
•    A systematic search that attempts to identify all the relevant studies (both published & unpublished)
•    A synthesis of the findings of the included studies
And it must also include a full methodology allowing for the searches and synthesis to be replicated.

There are numerous frameworks and guidlines for conducting sytematic reviews and it is likely that your supervisor will recommend one to you to be used as a roadmap for the project.

You can find links to the most commonly recommend frameworks on the right of this page

You should begin with some simple scoping searches.on the topic that you are looking at.  These will help identify how much research has already been done - and if there is enough evidence available for a systematic review to be possible.

The scoping search will also help you think about your research question and identify appropraite search terms.  You can do your scoping search in PubMed - or in one of our larger databases such as Scopus or Web of Science.  Google Scholar can also be useful here as it offers fulltext searching over a huge range of scholarly content.

It is also worth checking to see if a review has already been done.   The list below gives several palces that you can try in order to see if someone has already done a review in the area you are looking at -

Sources and Searching

You will need to search a range of sources for your review.  This is because you need to show that you have found all the research relevant to your topic. 

A good starting point for which databases to use is your subject guide - this will have the best databases for your subject area on the homepage.  While there is overlap in terms of what different databases contain they also all have unique content that you may miss if you don't search them.  It's also worth thinking about searching general databases that might have literature adjacent to your topic that could be useful. 

You should also consider searching for Grey Literature.  There is help on how to do this on our Key Web Resources page.


Our pages on how to do a literature search are a good starting point.

We have pages on Search Skills and on PICO Searching which will help you form your research question.

 You will need to do some initial broad searches to make sure that there is enough literature in the area you are looking at for a systematic review to be doable.

  • Defining your search terms: The best way to do this is to run a couple of wide searches on the most commonly used databases in your subject, for example PubMed. Find some relevant articles and read through them highlighting key words or phrases. You can then use these as the basis for your search strategy. Make a list of the core terms and any synonyms and spelling variations.
  • Thesaurus terms: The most precise way to search any database is to use the words included in the thesaurus for the individual database. As new articles are added to a database, they are indexed using a list of approved keywords or thesaurus. This is why advanced researchers always search one database at a time - remember that thesauri vary from database to database. Even natural language words can vary in the way they are used! Using this type of search usually produces very focused results.
  • Natural language searching: Sometimes you may need to use alternative keywords when searching. The research protocol may require you to widen out your search to ensure that you don't miss out any research. You will also find that many grey literature sources and search engines do not use thesauri, so you may have to use a combination of terms.
  • Advanced Filters: Some systematic searches also use advanced filters to enhance the focus a search, for example, to retrieve a particular study design or some other aspect of the research question. Advanced filters consist of a pre-tested combination of search terms and field codes that are translated for different databases. The Scottish Intercollegiate Guidelines Network (SIGN) have developed and adapted a number of filters for the development of clinical guidelines. The InterTASC Information Specialists’ Sub-group (ISSG) identifies, evaluates and tests search filters designed to retrieve research by study design or focus and includes filters for qualitative review.
  • Limits: Once the topic has been clearly defined, you should consider whether you want to limit the search by language or date of publication. This may be helpful when your topic is fairly new, but applying limits can miss out definitive older articles.

Remember - You can ask in the library for help with all of this.

You can book a 121 with a subject specialist by emailing

Keeping Track of it All

You will need to record your searches as part of the review.

It's a good idea to have a look at an existing systematic review to see how this is done - Cochrane reviews all have the search strategy recorded as an appendix at the end of the review.

If you have logins for the databases you are using (most of the resources we subscribe to will let you create these) then you can choose to save your searches this way.  Make sure you keep a record of which databases you used and when so you can easily find all the search data you'll need.

Another method is to record each search as you go along in a seperate document.  We recommend this as it also let's you see at a glance how many results each search got and track the differences in search results across resources.  This can help you pick which resources to focus on when doing your research.

You'll need to not only keep track of how you do your searching - but also the results you get.

You'll need to be able to remove duplicate results and to sort and evaluate your results so you can select the research that will form the basis of your review.

Bibliographic software allows you to manage all the references you need for your papers, report or thesis by enabling you to keep them in your own personal database or library. It allows you to:

  • Import references from databases or text files
  • insert citations into your document and automatically produce a bibliography in whatever style you require
  • you can build up your own database of relevant references
  • remove duplicate results and annotate your references

We recommend using Endnote as this is the bibliographic software that the library supports

You can get help with using Endote on our webpages - or by emailing to ask for a session with a subject specialist


Adapted from SMILE by Imperial College, Loughborough University and the University of Worcester, modified by Marion Kelt Glasgow Caledonian University which is licensed under a Creative Commons Attribution 4.0 International License.