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Systematic Reviews

Writing a Search Strategy

Writing a Search Strategy


In general, it is recommended that you work with a librarian to help you design comprehensive search strategies across a variety of databases. Writing a successful search strategy takes an intimate knowledge of bibliographic databases.  

Using boolean logic is an important component of writing a search strategy.  This can be tricky, because each database operates a little differently.  However, some general rules of thumb are that:

  • "AND" narrows the search
  • "OR" broadens the search 
  • "NOT" excludes terms
  • "*" finds all forms of a particular word
  • parentheses ensure all terms will be searched together as a set 
  • quotations around a phrase searches that exact phrase

3 Venn diagrams displaying the differences between the Boolean operators AND, OR, and NOT. Using AND narrows a search by requiring that both terms (puppy and kitten) be included in the results. Using OR broadens a search by requiring either term (puppy or kitten) be included in the results. Using NOT excludes just one term (kitten) so that included results only mention puppy and any results that mention kitten are excluded.

Search Strategy Template and Filters

Add the following lines to your search strategy with AND to filter for randomized controlled trials:

  • Highly Sensitive MEDLINE (via PubMed) Filter from Cochrane

(randomized controlled trial [pt] OR controlled clinical trial [pt] OR randomized [tiab] OR placebo [tiab] OR drug therapy [sh] OR randomly [tiab] OR trial [tiab] OR groups [tiab])

  • CINAHL Filter from SIGN

TX allocat* random* OR (MH "Quantitative Studies") OR (MH "Placebos") OR TX placebo* OR TX random* allocat* OR (MH "Random Assignment") OR TX randomi* control* trial* OR TX ( (singl* n1 blind*) OR (singl* n1 mask*) ) OR TX ( (doubl* n1 blind*) OR (doubl* n1 mask*) ) OR TX ( (tripl* n1 blind*) OR (tripl* n1 mask*) ) OR TX ( (trebl* n1 blind*) OR (trebl* n1 mask*) ) OR TX clinic* n1 trial* OR PT Clinical trial OR (MH "Clinical Trials+")

Sources and more information:

Add the following lines to your search strategy to include only human studies and exclude animal studies (line numbers are examples only, line 8 = final search strategy before addition of human studies filter):

MEDLINE (via PubMed)

8

#3 AND #6 AND #7

9

Animals[Mesh] NOT Humans[Mesh]

10

#8 NOT #9

CINAHL

8

#3 AND #6 AND #7

9

MH(Animals+ NOT Humans+)

10

#8 NOT #9

Cochrane Library

8

#3 AND #6 AND #7

9

MeSH descriptor: [Animals] explode all trees

10

MeSH descriptor: [Humans] explode all trees

11

#9 NOT #10

12

#8 NOT #11