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Systematic Reviews: Planning Your Search Strategy

Advanced Searching

Literature search template

A useful template to help with identifying the search terms from your question, and for grouping terms under the main concepts.   

Searching for and Selecting Studies

Planning a search

You should break down your question into its constituent concepts (e.g. using the PICO method outlined in Tip 3). Consider any synonyms and related terms for these key concepts in order to develop a search strategy. 

For good examples of search strategies used in systematic reviews see the Cochrane Database of Systematic Reviews (CDSR, part of the Cochrane Library) and the Database of Abstracts of Reviews of Effects (DARE). Most published systematic reviews include the full strategies used for each database, often in the appendices. You may be able to combine sections of strategies used in other reviews to form the basis of a good search strategy for your review.

Search free text using synonyms and truncation, and search in the title and abstract fields. All of these steps will increase the number of records retrieved. 

Test your draft strategy using papers that you are already aware of and would expect to find. If your strategy does not identify them, try to find out the reason and modify your search strategy accordingly.

Develop the strategy in one database and then translate it for other databases. If the databases use different controlled vocabularies you should adapt your descriptors but you should use the same free text terms.

You can limit your search strategy to different types of studies using search filters. AdThe ISSG Search Filter Resource lists a variety of these, though it can be difficult to use and does not provide access to the actual filters.

Try to reach a balance with the number of records retrieved by your search strategy. Your systematic review must be exhaustive but you also have to be realistic about the time and number of records that you are able to deal with.

When setting your limits, make sure you refer back to your protocol. Ensure that all your filter limits are applied with good reason, as established in your protocol.

PRESS Peer Review of Electronic Search Strategies

A useful checklist to improve the quality of your search strategy

Search tools

Selecting Databases to Search