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Systematic Reviews - Research Guide

Developing a Search Strategy

Search Strategies for Systematic Reviews

For a systematic review, you will need a systematic search strategy that attempts to identify all studies that would meet the eligibility criteria.

Not every concept in a systematic review topic or PICO protocol needs to be reflected in your search strategy. The structure of search strategies should be informed by the main concepts of the review by using only the appropriate elements from your PICO protocol or study design.

Search strategies usually concentrate on the following concepts:

  •  P = the patient or problem being addressed
  •  I = the intervention or exposure being considered
  • C = the comparison intervention or exposure where relevant
  • O = the clinical outcomes of interest
  • S = study design

Developing a Search Strategy

Once you have formulated your review topic, you can devise your search strategy:

Keyword and phrase search
Use the main concepts and keywords of the review topic, you have identified, as the basis of your search strategy. When searching for phrases, place your search terms in inverted commas - for example, "public health".

When creating a search strategy, consider synonyms for your keywords and group them together.

In some disciplines, you may need to combine keywords and phrases with controlled vocabulary terms to comprehensively describe your review topic.

Search the main concepts first, then limit further as necessary. Be aware of differences in American and English spelling and terminology. Most databases use American spelling and terminology as preferred subject terms.

Use connectors (Boolean operators)
Boolean operators connect phrases or keywords to improve your search results:

Operator Action Example


broadens your search showing results with at least one of your keywords paediatric OR children
AND narrows your search showing results which contain both keywords stress AND workplace
NOT narrows your search excluding certain words from your results rabies NOT dog

Use truncation and wildcard symbols

A truncator is used to retrieve the different ways a keyword might appear in a database. The symbol commonly used is the asterisk *. For example, develop* will retrieve develop, development, developments, developmental, developmentally, etc.

A wildcard replaces a letter within your keyword. For example, behavio?r will retrieve behaviour and behavior.  A wildcard can also be used where alternate spelling may contain an extra character, p?ediatric, will search paediatric or pediatric

Wildcard and truncation symbols vary from database to database. Check the database help section to identify the correct wildcard and truncation symbols.

Bring it all together
You can combine all the elements described above to create a search strategy:

Other database features
Many databases offer a variety of search features including limiting options, thesaurus buttons and field searching, which can enhance your search results. To find out what specific features a database offers, refer to its search help or tips.