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Search Biomedical Literature: A How-To Guide

Overview of steps and resources to assist researchers searching biomedical literature

Step 3: Write a Search Strategy

Write a Search Strategy

While it may be tempting to jump straight into your search, developing a strategy will save you time in the long run as it will help to ensure that you find studies relevant to your question. In general, it is recommended that you work with a librarian to help you design comprehensive search strategies. Contact UVic Libraries to request a consultation. 

  1. Revisit your research question to structure your search.
    The best way to search is to first break your research question down into its main concepts. This is where using a framework, such as a PICO, is useful. Which framework should I use?

  2. Brainstorm and gather synonyms for your research question's main concepts.
    Think broadly and abstractly!
    • Terms that have the same/close meaning
      • e.g. Hypertension vs High blood pressure
    • Terms that have different spellings or acronyms
      • e.g. Leukemia vs Leukaemia
    • Complex concepts described inconsistently
      • e.g. Long-term patient-reported satisfaction after contralateral prophylactic mastectomy vs surviving breast cancer: women’s experiences with their changed bodies
    • Umbrella terms and specific names
      • e.g. Sexually-transmitted infections vs herpes, genital warts, syphilis, gonorrhea, chlamydia
    • Keywords and database-specific “subject headings”
  3. Revisit the databases selected for the review
    The databases you choose will depend on your research question and the disciplines in which relevant research may be conducted. Librarians can also recommend databases to search for a systematic review. Contact UVic Libraries to request a consultation. Check UVic's Library's database catalog for a full list of available sources across all disciplines. Because every database works differently, different databases use the same syntax. 

    Dalhousie Search Syntax Guide - A cheat sheet for common health sciences databases
    More information on this topic can be found in B. Translate Search Strategies (see below).
  4. Construct the search string

    Writing a successful search string takes a knowledge of bibliographic databases. Several search techniques are common to a variety of licensed databases - subject headings, truncation, Boolean operators, and limiters. Depending on your topic, there may also be search filters available to apply to one or more databases. 

    Understanding Controlled Vocabularies

Controlled vocabularies are a set of predetermined terms that describe specific concepts. You will find that many databases use their own controlled vocabularies (sometimes called index termssubject headings, or a thesaurus). If you have heard of MeSH, this stands for Medical Subject Headings, and is the controlled vocabulary used in PubMed.

Databases that use controlled vocabularies employ subject specialists who review individual citations and add the appropriate controlled vocabulary terms to the citation that describe all of the concepts covered in the article. Using controlled vocabulary terms in your search strategy allows you to locate citations no matter what term(s) an author does or does not use, and helps account for spelling variations and acronyms.

Understanding Truncation

Understanding Boolean Operators

Understanding Limiters and Filters

Adapted and modified with gratitude from City University of London's Doing Post Graduate Research research guide and Dalhousie University's Systematic Reviews: A How-To Guide

Search Tips

Search Tips

Search with Keywords

Keywords are the words used in an article title, abstract, or other text field in a database. Keyword searching, or natural language searching, is how most people search for information and is often sufficient for most people. Keyword searching is also useful when attempting to identify literature that may not have been indexed with controlled vocabulary terms.

It is good practice to search with both controlled vocabulary and keywords because:

  • Not every database uses a controlled vocabulary (Scopus and Web of Science are two examples)
  • Each database has its own controlled vocabulary terms
  • If an article is too new, it may not be indexed with controlled vocabulary yet, and you would only find it with keywords
  • In PubMed, if an article is out of scope of MEDLINE, a component of PubMed, it may not ever be indexed with MeSH (PubMed's controlled vocabulary), and you would only find it with keywords
  • If an article lacks an abstract or additional author-supplied keywords, you may only find it with controlled vocabulary

If you want to be as comprehensive as possible, search with both controlled vocabulary and keywords.

Example: chronic kidney disease, chronic renal failure, CKD, CRF

Alternative Method for Finding Controlled Vocabulary Terms

  • Do a basic keyword search and choose a few citations that are relevant to your research question
  • Make a note of any keywords used in the article title or citation you may wish to add to your current list of keywords
  • Examine the full citation information for each article to find the controlled vocabulary terms assigned and write them down
  • Redo your search using both the controlled vocabulary and keyword terms

Avoid Stop Words

In bibliographic databases, stop words are words that the database has been programmed to ignore in a search string or query. Stop words include  of, the, is, at, which,and on.

Translate Search Strategies

Translate Search Strategies

Evidence synthesis methods require authors to search multiple databases, and not all databases accept the same search "syntax." Each individual database requires use of specialized search syntax, and therefore evidence synthesis search strategies must be 'translated' between databases.

When translating a search strategy from one database to another, you will have to make some changes to get comparable results. 

  1. Tailor every search strategy to each unique database, because within every database there are vendor/interface differences , subject headings versus keyword-only, peer-reviewed content only, and different controlled vocabularies. View Cornell University Libraries' Search Syntax Translation Examples.
    Database Controlled Vocabulary?
    CINAHL Yes, CINAHL Headings
    The Cochrane Library Yes, MeSH
    Embase Yes, Emtree
    ERIC Yes, Thesaurus
    Global Health Yes, Thesaurus (part of "Search Tools")
    PsycINFO Yes, Thesaurus
    PubMed Yes, MeSH
    Scopus No
    Web of Science No
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