Initial scoping searches, background reading, personal experience and input from the other members of the review team will all help to inform the search terms that you use in the final search strategy. You should consider synonyms, closely related terms, abbreviations and acronyms, alternative spellings and words with the same stem as you develop your search terms. Also, check the search strategies of related systematic reviews for the terms they have used.
You should use a combination of free text (or keyword) and subject heading (or thesaurus) terms. For an explanation of the difference between free text and thesaurus terms and how to search using both - read the book chapter below on free text and thesaurus searching.
Once you have identified your search terms you will need to make sure they are combined effectively using the Boolean operators AND, OR and NOT. If you need help planning your search strategy see the ‘Planning your search’, ‘Information Sources’ and ‘Searching effectively’ sections of your library subject guide. You may also need to use advanced search techniques such as proximity or adjacency searching. The help sections of individual databases provide guidance on how to do this.
Some systematic searches also use advanced filters to enhance the focus of 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 The ISSG search filter resource provides access to published and unpublished filters.
You should focus on one database while developing your final electronic search strategy but will then need to translate and apply it to multiple databases. Keep your thesaurus terms as consistent as possible and always use the same free text terms across all of the databases.
You can also get support with developing your search strategy from your librarian.
To make sure that your search strategy is consistent across all the databases you are using, you will need to understand any differences that exist to how they each apply Boolean operators, adjacency (or proximity operators) and search symbols such as truncation, wildcard and phrase searching. You can find this information in the help section of the individual databases you are using. You can also use this handy database syntax guide that pulls together this information for most of the major databases.