Skip to main content

Systematic and Scoping Reviews Search Methodology

Search 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 Ovid tutorials 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.

Subject Headings

Many databases include a system of subject headings (which may also be called descriptors). These terms are added to articles by human indexers to make it easier to search for all the articles on a particular concept. MeSH (Medical Subject Headings) are used in MEDLINE. EMBASE, CINAHL, and many other databases have their own systems of subject headings; these can usually be found in the thesaurus section of a database.

Keywords

For a thorough literature search, you should search with both keywords and subject headings. Some databases or grey literature search sources only allow searching by keyword. 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.

  • Example: child* searches for child, child's, children, childhood... anything that begins with "child".

 

Most databases support searching for exact phrases by putting words in quotes. 

 

Some databases allow adjacency searching, which will find words close to each other, but in any order.

  • Example: In Ovid MEDLINE, social adj3 support will find the words social and support within 3 words of each other.

 

Check the help section of the database you're using to find out which of these features are available and how to use them.

Tutorials and Handouts

Boolean Operators

Boolean operators are useful for combining subject headings and keywords.

 

  • Example: Stroke AND balance finds articles with both these concepts
  • Example: Stroke OR CVA finds articles that include either or both concepts

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

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, study design, or type of publication. 

Consult with a librarian about using limits in a systematic review search - it's easy to lose relevant articles when adding limits. 

One way to limit to human studies in Ovid MEDLINE is to combine this line with the last set of your search:

NOT (exp animals/ NOT (exp animals/ AND humans/)

How and when to use study type filters from Countway Library of Medicine, Harvard http://guides.library.harvard.edu/c.php?g=309982&p=2070466

Example Ovid MEDLINE search strategy

This document shows a sample search strategy and explains it with reference to the PICO model.

Search Filters

Search filters are pre-tested strategies used to find evidence in the medical databases that meets given criteria. They are often used to locate a specific type of study, such as a randomized controlled trial or a qualitative study. Use search filters to increase the chance of finding relevant materials.