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Systematic Reviews (in the Health Sciences)

Guidance for conducting health sciences systematic reviews.

This page includes information on search techniques for searching databases. View the Search Development page of this guide for guidance on how to use these techniques to develop a SR search strategy.

Search Techniques

Searches are typically organized using the Boolean operators OR or AND. OR is used to combine synonyms and related terms for the same concept  AND is used to combine different concepts.

Example: Living Donor AND Deceased Donor

Example: Living Donor OR Deceased Donor

The blue in both images represents the article retrieved. Using AND to combine the two search terms will only retrieve results where both terms are used. Using OR to combine the two search terms will retrieve results that use either term separately or both together.

Include controlled vocabulary for applicable databases. Not all databases have controlled vocabulary (also known as subject searching). The following are common databases used in health sciences research that have controlled vocabulary. This is not a comprehensive list. Check each database for controlled vocabulary ability and consult the database help section for help using controlled vocabulary. 

Controlled Vocabulary
Database Controlled Vocabulary Example
PubMed (Medline) Medical Subject Headings (MeSH) "Sexual and Gender Minorities"[Mesh]
Ovid Medline Medical Subject Headings (MeSH) "Sexual and Gender Minorities"/
Embase EMTREE 'sexual and gender minority'/exp
CINAHL CINAHL Headings (MH "GLBT Persons+")
ERIC (via EBSCO) ERIC Thesaurus DE "Homosexuality"

Proximity searching is a way to search for two or more words that occur within a certain number of words from each other. There may be some cases in which proximity searching would be helpful. Below are some examples. Please refer to the help section of the database. 

Proximity Searching
Databases Proximity Indicator Example
PubMed [field:~N] "hip pain"[Title/Abstract:~2]
Ovid Medline ADJ# multisensory ADJ8 environment


NEXT/# (specific order)
multisensory NEAR/8 environment
Cochrane Library Not possible N/A


W# (specific order)
multisensory N8 environment
Web of Science NEAR/# multisensory NEAR/8 environment

NEAR/# or n/#

PRE/# or p/# (specific order)
multisensory NEAR/8 environment

More Search Techniques


  • Database limits are database-provided limit features that allow users to narrow results based on criteria, such as language, publication type, publication date, etc. 
  • Database limits are generally NOT recommended for use in systematic reviews, due to their fallibility, unless there is justification provided. 
  • For example, for example if you want to limit your search results by date, you need a good reason to do so and must explain your reasoning in your protocol and manuscript. 

For a more detailed explanation, see ITEM 3: LIMITS AND RESTRICTIONS of the PRISMA-S Explanation and Elaboration document. 

Hedges or filters are published search strategies developed by experts and are typically validated. Hedges are often used to narrow results by specific study designs, publication types, population, or topic. 

For a more detailed explanation, see ITEM 4: SEARCH FILTERS of the PRISMA-S Explanation and Elaboration document. 

Truncation or wildcards are techniques that broadens your search to include various word endings or word variations or spellings. Typical search symbols include the asterisk (*), used to replace one or more characters, usually at the end of the word, and the question mark (?), used to replace a single character, either inside or at the end of the word. 

For example:

  1. toxic* retrieves toxic, toxicity, toxicology, etc. 
  2. behavio?r retrieves behaviour and behavior
  3. p?diatric retrieves pediatric and paediatric


  • Each database has unique rules. View the help section of each database for instructions on how to search with truncation and wildcards.
  • In some instances, it may be better to use the various versions of the word instead of truncation. It depends on the word, word variations, and specific database. 
  • Test your search in each database with and without truncation before making a decision on which strategy is best for your search. 

A phrase search will search for two or more words as an exact phrase. To do so, enclose the words in quotation marks. 

For example: "cultural humility." 

If you are considering using phrase searching for an SR search, compare your strategy with and without phrase searching in order to determine if you would miss relevant literature using phrase searching.