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Researching for your literature review: Activity: Subject searching

Understanding subject headings

Subject searching tips:

  • Subject headings are assigned based on the topic of the article (rather than the words used in the title or abstract).
  • A database will only search for subject headings in the 'subject field' of database records.
  • You can also browse subject headings on your topic and locate broader or narrower terms, as subject headings are contained within the controlled vocabulary or thesaurus. (For medical subject headings this is known as the MeSH tree).
  • Subject heading searching increases the relevance of search results, and when combined with keyword searching is a more advanced method suitable for comprehensive searches.
  • Subject headings are not available for every topic and it is best to only select them if they relate closely to your research question.

Some key terminology and features of MeSH:

  • MeSH stands for Medical Subject Heading, and are applied to every article in Medline by professional indexers.
  • Because of the branching structure of the subject heading hierarchies, the controlled vocabulary is referred to as the MeSH tree.
  • The Scope note provides a definition of the subject heading, as well as other key information.
  • If you explode a subject heading you will retrieve all of the narrower, more specific subject headings that sit indented below it on the tree (Not all headings have narrower terms, therefore not all can be exploded).
  • If you focus a subject heading you limit your search to only those documents in which your subject heading is listed as a major focus of the article. (This is not recommended for comprehensive searches as the indexer may not have selected the heading as a major focus).
  • Subheadings (sometimes called qualifiers) may be used in combination with MeSH headings, and are used to describe the specific aspects of the MeSH heading that are pertinent to the article. (Comprehensive searches often simply include all subheadings).

Subject searching in Ovid Medline


An Ovid Medline record in the Complete Reference format is shown below. Note the list of MeSH subject headings assigned to the article.

screenshot of an Ovid Medline record with the Complete Reference link circled

screenshot of the MeSH Subject Headings in a Medline record

 

Activity: Search by subject heading

Key databases such as Ovid Medline allow you to do a subject heading search to locate relevant subject headings for your key concepts.

1.  Login to Ovid Medline at http://guides.lib.monash.edu/go.php?c=8479877

2.  Enter infection control, tick the Map Term to Subject Heading box, and click Search.

screenshot of infection control in the Medline search box and the Map Term to Subject Heading option selected

Your search term is mapped to a Medical Subject Heading (MeSH) if possible. Infection control is a MESH subject heading.

Click on the Scope note next to Infection control for more details including a definition of this term. Look for any synonyms listed under Used for. After confirming it is appropriate for your topic, click on the subject heading link.

screenshot of the search result showing that infection control is a MeSH heading


The subject heading tree is displayed. Look for any relevant narrower or broader terms for Infection control and select all that apply. The narrower terms are easily identifiable as they are indented to the right below a term. If you wish to select ALL narrower terms, tick the Explode button. In this example we will explode Infection Control.

screenshot of the MeSH tree for infection control showing the narrower terms and the Explode function highlighted


Then scroll to the top of the page to click Continue. A list of subheadings is displayed. Click Continue to Include All Subheadings by default.

screenshot of the subheadings for infection control with the Continue button highlighted

3.  Enter methicillin resistant staphylococcus aureus, ensure the Map Term to Subject Heading box is ticked, and click Search.

screenshot of methicillin resistant staphylococcus aureus in the Medline search box and the Map Term to Subject Heading option selected

Methicillin-resistant staphylococcus aureus is listed as a subject heading. Because the MeSH heading has a hyphen in it and we didn't search it that way, we see a number of suggested headings. When there is not an exact match, Ovid looks for records where the term appears in fields such as the title or abstract, and retrieves frequently occurring subject headings in those records. In a frequency-based list, one heading might be appropriate, or several, or none.
In this list, notice that Staphylococcus aureus and Methicillin resistance also appear on their own as other MeSH headings. Click on the Scope note for further information. If combined these headings are also relevant, so make a note to include these in the next search.
Click on the Methicillin-resistant staphylococcus aureus link.

screenshot of the search result showing that Methicillin-Resistant Staphylococcus aureus is a MeSH term


A section of the subject heading tree is displayed. In this instance there are no narrower terms indented underneath Methicillin-resistant staphylococcus aureus, so exploding the heading will not achieve anything. Ensure Methicillin-resistant staphylococcus aureus is ticked and click Continue.

screenshot of Methicillin-Resistant Staphylococcus aureus in the tree


A list of subheadings is displayed. Click Continue to Include All Subheadings by default.

screenshot of the subheadings for Methiciliin-Resistant Staphylococcus aureus with the Continue button highlighted


4.
Now repeat the search for Methicillin-resistant staphylococcus aureus as this is how you located the other relevant headings. Tick  Staphylococcus aureus and then tick Methicillin resistance. We won't visit the tree for these individually as we want them combined. Use the drop-down menu above to combine them with AND then click Continue. This will only retrieve articles in which both subject headings are present.

screenshot of the two MeSH terms Staphylococcus aureus and Methicillin Resistance combined with AND


5.  Enter aged care homes, ensure the Map Term to Subject Heading box is ticked, and click Search.

screenshot of aged care homes in the Medline search box and the Map Term to Subject Heading option selected


There is no subject heading for aged care homes so again we see a frequency based listing. This includes Homes for the Aged as well as Nursing Homes. Look at the Scope notes for more information. Click Homes for the Aged to view it in the tree. 

screenshot showing that the MeSH term is Homes for the Aged


In the tree we can see it comes under the broader term Residential Facilities and there are no narrower terms. Scroll to the top of the page and click Continue.

screenshot showing Homes for the Aged in the tree


A list of subheadings is displayed. Click Continue to Include All Subheadings by default.

screenshot showing the subheadings for Homes for the Aged and the Continue button highlighted


6.  Enter Nursing homes, ensure the Map Term to Subject Heading box is ticked, and click Search

screenshot of nursing homes in the Medline search box and the Map Term to Subject Heading option selected


Click Nursing Homes to view it in the tree. 

screenshot of results showing that nursing homes is a MeSH term


We can see that Nursing Homes has narrower terms. Look at the Scope note to see if these are relevant to include. To only search on Nursing Homes scroll to the top of the page and click Continue.

screenshot of Nursing Homes in the tree showing it has narrower terms


A list of subheadings is displayed. Click Continue to Include All Subheadings by default.

screenshot of the subheadings for Nursing Homes and the Continue button highlighted


Now you have completed your subject heading searches, you could try combining them in your Search history.

Go to the Search history and combine any results related to the same concept with OR

screenshot of the Search History in Medline highlighting the OR button for combining terms within each concept


Then combine all the search sets from each concept with AND

screenshot of the Search History with showing how to combine concepts with AND


Now you will be able to see the final number of search results from this search. Scroll down to see the search results displayed, or apply any Limits. Remember this is not a comprehensive search as we have not yet included our keyword searches.

screenshot of Search History now combined with 52 results


7.  Tick the English language limit, and then click Search. This limits the last search result in the Search History. There are many more limits available if you click on the Additional limits button.

screenshot showing the English limit selected and highlighting the button for Additional limits


8.  Review your results and refine your search as necessary. Note that the results are listed in order from newest to oldest (not relevance).

Tip: For articles that are particularly relevant to your topic, ensure to look at the Complete reference in Ovid Medline to see which MeSH have been applied to the article. You may find relevant MeSH that you can add to your own search strategy.