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Researching for your literature review: 4. Search strategy

Search strategy process

search strategy process

Database operators

reading  Database operators - quick reference guide

Includes database operators such as boolean, proximity operators, phrase searching, truncation symbols, wildcards and subject headings.

Online tutorial - Developing a database search strategy

Developing a search strategy

Start developing a search strategy by identifying the key words and concepts within your research question. 

For example: What strategies can healthcare workers use to communicate effectively with clients with a hearing disability?

Treat each component as a separate concept (there are usually between 2-4 concepts).

For each concept list the key words derived from your research question, as well as any other relevant terms or synonyms that you have found in your preliminary searches. Also consider singular and plural forms of words, variant spellings, acronyms and relevant index terms (subject headings).

While the term strategies has been identified as a concept in this example, there are likely to be relevant articles that do not include terms such as strategies. As such, this concept would not be included in the final search strategy.

Search concept 1 Search concept 2 Search concept 3 Search concept 4
strategies healthcare workers communication hearing disability
methods healthcare professionals communicating hearing impairment
  health personnel interpersonal communication hearing impaired
health professional communication skills deaf
Combine search terms with OR / AND / NOT (Boolean operators)

boolean operators


  • Link keywords related to a single concept with OR
  • Linking with OR broadens a search (increases the number of results) by searching for any of the alternative keywords

Example: hearing impaired OR deaf


  • Link different concepts with AND
  • Linking with AND narrows a search (reduces the number of results) by retrieving only those records that include all of your specified keywords

Example: hearing impaired AND communication


  • using NOT narrows a search by excluding certain search terms
  • Most searches do not require the use of the NOT operator

Example: hearing impaired NOT deaf will retrieve all results that include the words hearing impaired but don’t contain the word deaf.

Use symbols to retrieve word variations

Truncation and Wildcard

Truncation - The truncation symbol is commonly an asterisk * and is added at the end of a word.

  • The asterisk applied to the root of a word captures other endings to that root word making it useful for retrieving singular, plural and other variations of a keyword.

Example:  strateg* will retrieve strategy, strategies, strategic, strategize etc

Note: If you don't want to retrieve all possible variations, an easy alternative is to utilise the OR operator instead e.g. strategy OR strategies.

Wildcard  - Wildcard symbols include the question mark ? and hash #. They replace zero, one or more characters in the middle of a word.

Example:  wom#n finds woman or women, p?ediatric finds pediatric or paediatric.

The symbols may vary in different databases - See the Database operators guide on the left for details or check the Help link in any database.

Use quotes to keep word order when searching for phrases

For phrase searching, place two or more words in "inverted commas" or "quote marks".

Example:   “hearing impaired”

In some databases, words may be searched separately if the quote marks are not used. In other databases, word order may be maintained without the need for quote marks.

See the Database operators guide for details on phrase searching in key databases, or check the Help link in any database.

Identify appropriate Subject Headings (index terms)

Many databases use subject headings to index content. These are generally selected from a controlled list by experienced indexers (people - not machines!) and describe what the article is about. 

A comprehensive search strategy is often best achieved by using a combination of keywords and subject headings where possible.

In-depth knowledge of subject headings is not required for users to benefit from improved search performance using them in their searches.

Advantages of subject searching:

  • Helps locate articles that use synonyms, variant spellings, plurals
  • Search terms don’t have to appear in the title or abstract

Note: Subject headings are often unique to a particular database, so you will need to look for appropriate subject headings in each database you intend to use.

Subject headings are not available for every topic, and it is best to only select them if they relate closely to your area of interest. 

MeSH (Medical Subject Headings)

The MeSH thesaurus provides standard terminology, imposing uniformity and consistency on the indexing of biomedical literature. In Pubmed/Medline each record is tagged with MeSH (Medical Subject Headings).

The MeSH vocabulary includes:

  • Headings (also called main headings or descriptors)
    • Represent concepts found in the biomedical literature
    • Some headings are commonly considered for every article (eg. Species (including humans), Sex, Age groups (for humans), Historical time periods)
  • Subheadings (also called qualifiers)
    • attached to MeSH headings to describe a specific aspect of a concept
  • Publication characteristics/types
    • describe the type of publication being indexed; i.e., what the item is, not what the article is about (eg. Letter, Review, Randomized Controlled Trial)
  • Supplementary concept records
    • Terms in a separate thesaurus, primarily substance terms


Identify useful limits

Many databases provide system based limits. Adding a limit to a search will exclude certain material not relevant to your research question, and therefore reduce the number of results.

Examples include:

  • limiting to English language
  • limiting by publication date
  • limiting to a specific document type
  • limiting your search to specific fields, such as only searching in the Title/Abstract fields

The use of limits should be justified by the focus of your research and any constraints.

It is useful to build a ‘sample set’ or ‘gold set’ of relevant references before you develop your search strategy.

Sources for a 'sample set' may include:

  • Key papers recommended by subject experts or supervisors
  • Citation searching - looking at a reference list to see who has been cited, or using a citation database (eg. Scopus, Web of Science) to see who has cited a known relevant article.
  • Results of preliminary scoping searches

The papers in your 'sample set' can then be used to help you identify relevant search terms

  • Look up your 'sample set' articles in a database that you will use for your literature review. For the articles indexed in the database, look at the records to see what keywords and/or subject headings are listed.

The 'sample set' will also provide a means of testing your search strategy

  • When an indexed article is not retrieved, your search strategy can be revised in order to include it (see what concepts or keywords can be incorporated into your search strategy so that the article is retrieved).
  • If your search strategy is retrieving a lot of irrelevant results, look at the irrelevant records to determine why they are being retrieved. What keywords or subject headings are causing them to appear? Can you change these without losing any relevant articles from your results?
An example of a search strategy that could be applied to different databases is shown below

sample search strategy

The above search strategy in a nested format (for use in a single search box) would look like:

("healthcare worker*" OR "health care worker*" OR "healthcare professional*" OR "health professional*" OR "health personnel") AND (communicat* OR "interpersonal communication" OR "communication skill*") AND ("hearing disabilit*" OR "hearing impair*" OR deaf* OR "hard of hearing" OR "hearing loss")

reading    Appraising the quality of your search strategy: checklist

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