Evidence-Based Practice: Search Tips

Two quick ways to start searching for your topic:

• Look to see if the database has an online thesaurus or subject headings to browse for the key terms in your topic. In PubMed, the thesaurus is called MeSH (Medical Subject Headings); in other databases you may see the term "Headings." When in doubt, check the Help screens.

                           - OR -

• Start with a keyword search, using words/phrases that describe your topic.

• Browse the results; choose 2 or 3 that are relevant.

• Look at the Subject Headings or Descriptor field and note the terms used.

• Incorporate those new terms into your search.

• Your results will often be more precise than your initial keyword search.

Most databases offer filters or limits for type of study. For instance, when searching for Level 1 evidence on your topic, you may be able to select systematic review and/or randomized controlled trial so that only those types of studies will appear in your result list.

Subject headings describe the content of each item in a database. Use these headings to find relevant items on the same topic. Searching by subject headings (a.k.a. descriptors) is the most precise way to search within article databases.

Keyword searching is how you typically search the Web. Think of important words or phrases and type them in the search box to get results.

Here are some key points about each type of search:

Use AND in a search to:

• narrow your results

• tell the database that ALL search terms must be present in the resulting records

• example: cloning AND humans AND ethics

The purple triangle in the middle of the Venn diagram below represents the result set for this search. It is a small set using AND, the combination of all three search words.

Use OR in a search to:

• connect two or more similar concepts (synonyms)

• broaden your results, telling the database that ANY of your search terms can be present in the resulting records

• example: cloning OR genetics OR reproduction

All three circles represent the result set for this search. It is a big set because any of those words are valid using the OR operator.

Use NOT in a search to:

• exclude words from your search

• narrow your search, telling the database to ignore concepts that may be implied by your search terms

• example:  dementia NOT alzheimer's

Use parentheses to combine search strings:

If you use more than one type of connector in a search statement, e.g. AND as well as OR, you need to use parentheses to keep the groups of terms together when using one search box. This procedure is sometimes called nesting. For example:

• (women OR woman OR female) AND (smoking OR tobacco)

Another option is to use the Advanced Search screen where you can often combine your different terms and connectors in multiple search boxes.

Phrase Searching

Most databases allow you to specify that adjacent words be searched as phrases:

• Using parentheses or quotes around search words is a common way to find an exact phrase. Example:  "genetic engineering"

• However, not all databases or search engines recognize phrase searching. One alternate method is to use the Advanced Search screen, where you can often specify that you want your words searched as an exact phrase.

Proximity Searching

Some databases allow you to use proximity operators to find more relevant results. Rather than an exact phrase, a proximity search will find words near each other within an article or record. Proximity operators vary by database, but here are some common examples:

• w# = with
• Specifies that words appear in the order you type them in.

• Substitute the # with a number of words that may appear in between. If no number is given, then it specifies an exact phrase.

• Examples:
  genetic w engineering (searches the phrase genetic engineering)
  genetic w3 engineering (retrieves genetic engineering, genetic and biological engineering, etc.)

• n# = near
• Specifies that the words may appear in any order.

• Substitute the # with a number of words that may appear in between.

• Examples:
  cloning n3 human (retrieves cloning of humans, human cloning etc.)

Truncation

Truncation, also called stemming, is a technique that broadens your search to include various word endings and spellings.

• To use truncation, enter the root of a word and put the truncation symbol at the end.

• The database will return results that include any ending of that root word.

• Examples:
  child* = child, childs, children, childrens, childhood
  genetic* = genetic, genetics, genetically

• Truncation symbols may vary by database; common symbols include: *, !, ?, or #

Wildcards

Similar to truncation, wildcards substitute a symbol for one letter of a word.

• This is useful if a word is spelled in different ways, but still has the same meaning.
  
  
• Examples:
  wom!n = woman, women
  colo?r = color, colour

When using any of the above search tips, you may have to first consult the database Help screens to find out which words or symbols are recognized in that particular database. 

If you have questions about applying any of these techniques to your search, please Ask Us!

To limit your search results to a subset of journals in PubMed, use the following journal filters (copy and paste the list of titles into the search box and combine with your other search terms).

Contact a librarian if you would like some help searching for information on your topic or tracking down the full text of an article. That's why we're here!