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Good review practice: a researcher guide to systematic review methodology in the sciences of food and health

Identifying search terms

Identifying search terms

The eligibility criteria guide the scope of the review and can help in identifying terms to develop search strategies and find relevant evidence.  The framework identifies the key concepts that will make up the search—e.g. What is the population, and what is the exposure? —but it identifies only one term for each concept.  To comprehensively locate all relevant studies all applicable variations of these terms must be identified so that they can be incorporated into the search.   

For example, if the original term identified was poultry, the search string could expand this to poultry OR fowl OR chicken* OR chukar* OR duck* OR emu OR emus OR goose OR geese OR "guinea fowl*" OR ostriche* OR quail* OR rea OR rheas OR turkey* OR waterfowl.

[Note that some terms such as emu should not be truncated since truncation would introduce many inappropriate terms like emulsify or emulate.  Learn more in the supplementary materials].

How to identify search terms

Prior experience, consultation with subject experts in the review team or beyond it, exploring database controlled vocabulary, and running searches and scrutinizing the results are all important appropriate approaches for finding search terms.  

Key articles.  A close reading of the key articles will yield many search terms, which can be the seeds for a search strategy.  Looking at the records for the articles as they have been indexed across databases will give insight into the subject headings used in different databases.  Controlled vocabulary lists, or thesauri, within databases include additional terms, related terms, and broader and narrower terms for their entries.  These lists are powerful tools for identifying additional terms. 

Expertise:  a librarian familiar with a topic area might have good basis of knowledge about the range of terms representing a particular concept in the literature.  Team subject experts will also be familiar with appropriate terminology.  If a librarian builds the search string for the team, they will always consult closely with the rest of the team to be sure that the string is capturing what is needed.  

Search iterations:  as a search string is being built and tried, new terms will often be found in the records returned.  Other desirable adjustments can also become apparent:  a term might consistently be used in a different sense than intended or a term's truncation point might be too early or too late.

Scoping Study: if a scoping study has been conducted to test the volume of the studies available, then a searcher will have an additional collection of records that are highly relevant to the question.   Titles, abstracts, and subject headings of these records can yield additional relevant terms.