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Systematic Review: 1. Design search

What is searching?


Once you have developed a focused question and considered your inclusion and exclusion criteria you need to create an effective and efficient search process to retrieve all relevant evidence from a range of sources.

Searching is an iterative process. You will need to develop a search and continually review and refine it for constant improvement.

Create a sample set

It is useful to build a 'gold set'  of relevant references before you develop your search strategy.  The papers in your 'gold set' can then be used to help you identify relevant search terms and to test that your search strategy will retrieve these items and other relevant references on your topic.

Sources for this 'gold set' may include:

  • Key papers recommended by subject experts or your supervisor

  • Citation searching ('pearl growing' or 'snowballing') techniques to locate further relevant references cited in or by key papers

  • References used in similar systematic reviews

Develop a search strategy

A comprehensive search would usually entail a combination of subject headings , plus a wide range of keywords/phrases  for each concept.  

Not all databases will have subject heading searching and for those that do, the subject heading categories may differ between databases. This is because databases classify articles using different criteria.

Identifying relevant keywords and subject headings

Concept map


You may create a concept map to list the subjects and key terms that you have identified.  This list can be quite extensive and it can be helpful to use an Excel spreadsheet.

  • The concept map/grid may change after you have done some test searches.  You may also discover new or different ideas as you explore the subjects and look for more clues.


Example of a concept map/grid
   Accessibility document - Concept Map/Grid


  Using text mining for study identification in systematic reviews: a systematic review of current approaches 

Combining and truncating search terms

Boolean operators

Boolean operators are used to combine the different concepts in your topic (or the elements in your PICO question).

The operators that are used to combine terms in a search strategy are AND, OR, NOT.


Boolean operators


    Accessibility document - how to use Boolean Operators


    Database search tips - reference guide 

   Pubvenn - tool to help you practice boolean logic 


Proximity Operators

Proximity operators are extremely useful when looking for combinations of keywords in a phrase.


Proximity operators


    Accessibility document - How to use Proximity operators


    Database search tips - reference guide 

Truncation and wildcards

When using keywords, consider the need for Truncation and Wildcards to capture all relevant research.  These can be used to ensure you retrieve any keyword variations, such as synonyms, plurals and variant endings and spellings.


Truncation and Wildcard
    Accessibility document - Using truncation and wildcards

    Database search tips - reference guide