Western Libraries

Knowledge Synthesis: Systematic & Scoping Reviews

Searching Techniques

Several search techniques are common to a variety of licensed databases - subject headings, truncation, Boolean operators, and limits. Depending on your topic, there may also be search filters available to apply to one or more databases. See these Medline OvidSP tutorials (from UBC) for an overview. You may find it helpful to use a table in Word or Excel to track the subject headings and keywords you've used for concepts. Also, most licensed databases include an option to save your search history, and to set up email alerts when new articles are found on your topic.

Step by Step

  1. Select your database
  2. Break you question into concepts
  3. Identify subject headings for each concept
  4. Identify text words for each concept


  • Use a “target article” to help identify search terms
  • Use a worksheet to keep track of your terms

Subject Headings

Database Subject Headings
Medline/PubMed MESH
Cochrane Library MeSH
PsychINFO Thesaurus of Psychological Index Terms
Scopus & Web of Science N/A
IEEEXplore N/A


  • Select subject headings that are the closest match for your concepts
  • Pay attention to “explode” commands – PubMed will search related headings by default


To ensure you are conducting a comprehensive literature search, you should search using a combination of keywords as well as subject headings. Some databases have subject headings and some you have to search using keywords.  A useful technique to utilize in keyword searching is truncation (or wildcards). This is when you use a character at the end or within a word to search for different spellings. Many databases use * as the truncation symbol.

OVID search commands for Text Word or Keyword Searching


  • Keywords are very useful when searching recent articles that may not not been given subject headings as yet or articles published prior to subject heading identifiers.
  • Check the help section of the database you're using to find out which of these features are available and how to use them.
Operator Command Example
* Find alternate endings

hosp* [will find hospital, hospitals, hospitalist, hospice, hospices, etc.]

.tw. Search for this term in the Title & Abstract fields


ADJ Search for one term within x number of terms from another patient adj3 anxiety [will find patient within three words of anxiety]
AND Find articles where both terms appear

smoking AND cessation

OR Find articles where either term appears

smoking OR tobacco

() Control order of operations - commands within brackets run first

(smok* OR tobacco).tw.

Limit or Refine

Most databases include various limiters. These usually qualify human characteristics such as gender, ethnicity or age or publication characteristics such as language, publication date, or type of publication. 

A few useful ones in MEDLINE include human; English language; review article; male or female; and limits for various age groups.

Boolean operators

Boolean operators are useful for combining subject headings and keywords.

AND, OR, NOT are the Boolean operators to use to combine searches

image from http://uksourcers.co.uk/wp-content/uploads/2012/06/Boolean-Ven.jpg 

  • Boolean operators should be entered in uppercase letters 
  • Combining with OR will produce more results
  • Combine concepts with AND will produce fewer results
  • Combine with NOT will eliminate unwanted results

NOT is another operator which will find one concept while excluding another. Use with caution because you may exclude relevant articles this way.

A few more tips

  • Use of appropriate synonyms, acronyms, etc.
  • Use of all appropriate subject heading/controlled vocabulary terms across each database.
  • Use of keywords/text words  in addition to controlled vocabulary terms.
  • Appropriate use of explosion, subheadings, and floating subheadings.
  • Use Truncation and spelling variation as appropriate.
  • Boolean operators used appropriately..
  • Inclusion of grey literature sources if applicable