Subject Headings
on OvidSP Medline and Embase
and
The Cochrane Library
Subject Headings, such as MeSH (Medical Subject Headings) as used in databases such as Medline, are
assigned by the database producers to individual records on the database. A Subject Heading List or
Thesaurus uses controlled language i.e. pre-specified terms (rather than random terms, variants of
terms and spellings) to describe and categorise records. The Thesaurus is then used to specify the
subjects covered by a record within a database and thus allows more controlled searching than
keyword searching.
Medline, Embase and The Cochrane Library all use different Subject Heading systems with differing
functionality.
Some search interfaces will ‘map’ search terms to Subject Headings so that even if the term you have
searched for is not listed it will usually refer you to a Subject Heading/s which is used for that term.
Freetext (Keyword/non-Subject Heading) searching will search for results throughout pre-specified
fields automatically usually including author, title abstract and sometimes the full text.
In most circumstances you would use both the freetext and Subject Heading search options to
optimise your search.
Searching using Subject Headings
When searching using Subject Headings you should enter a single word or phrase at a time only. You
should not use Boolean within a Subject Heading search statement. Individual Subject Heading
searches can be combined using Boolean at a later stage.
Subheadings and Qualifiers
There are normally various standard subheadings which can be selected for all the Subject Heading
terms in a given database which are used to indicate aspects of a topic e.g. adverse effects, diagnosis,
therapy. These are known as Subheadings on Ovid Medline and Embase and as Qualifiers on The
Cochrane Library.
Subject Headings on Ovid Medline and Embase
Medline is produced by the U.S National Library of Medicine (NLM). The NLM use Medical Subject
Headings (MeSH) to describe the contents of the articles it is indexing. EMBASE is produced by
the publisher Elsevier Science who use the EMTREE Thesaurus for the database Subject Headings.
Both database Subject Heading systems, however function in similar ways:
To access the Subject Headings search option in the Advanced Search on Ovid Medline, tick the
checkbox next to Map Term to Subject Heading and enter your word/phrase in the search box.
On the following screen the Mapping Display screen provides a list of possible Subject Headings for
this topic. Click in the checkbox to the left of any headings given to select them - and unclick on any
headings to deselect them.
Take for example a search on Biopsy, a mapping display for this Subject Heading search will retrieve a
list of possible subject headings. You may wish to select Biopsy, fine needle. To do this you would:
 Tick the checkbox to the left of this heading to select it
 Untick the box for biopsy
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You can now choose to select all the standard subheadings offered by clicking on the Include All
Subheadings option or you can select Continue. If you select Continue you will then be presented
with a list of standard subheadings from which you can select the ones you wish to use or select the
repeated All Subheadings option.
The Thesaurus Tree
After entering a term to map to Subject Headings you can select any individual term by clicking on it
to view its position on the Thesaurus tree. The Thesaurus tree allows you to view where a Subject
Heading is placed within the Thesaurus ‘tree’. The tree illustrates the hierarchies and relationships of
the different Thesaurus terms. You can therefore use it to clarify and select Subject Heading terms.
In the tree the nearest match will be highlighted in blue. Indented items listed below this will be more
specific headings than your Subject Heading term.
As an example, from the main search page type in breast cancer (selecting to map the term to subject
headings).
The subject heading maps to Breast neoplasms. To check this term’s position in the Thesaurus tree
you would simply click on it. This would display the Tree structure.
Scanning down the Tree you will see that the term Breast Neoplasms (highlighted in blue) is part of the
Diseases - Neoplasms tree. Terms such as Breast Neoplasms, Male and Carcinoma, Ductal, Breast are
indented under Breast Neoplasms as more specific Subject Headings relating to that Heading.
Exploding, Focus and Scope
You will also see the following options on a Mapping Display or retrieved Tree screen:
 Explode: will search for the term you have selected and all the subcategories of that term
indented below. This is a very useful option.
 Focus: will retrieve articles where your selected subject heading is the major topic.
 Scope: is not a search ‘option’. However it is very useful as it gives the Subject Heading
limits and definitions of a particular term as used in this particular database
If you wish to use either the Explode or Focus option, select and click on Continue to return to the
main search screen.
This sheet forms part of HYMS Information Skills 3
Subject Headings on the Cochrane Library
The Cochrane Subject Heading Thesaurus is based on that of the National Library of Medicine (NLM)
MeSH.
Note: Although the Cochrane Library is an invaluable, core resource, providing high
quality information over 6 databases, the functionality of the MeSH option within it is
limited and coverage not complete. Not all records include Subject Headings.
To access the MeSH search option on the Cochrane click on the Advanced Search option and then
select the Medical Terms (MeSH Search) option. Enter your search term and select Lookup.
You will then see a screen with the following sections:



Definition: see how the Cochrane MeSH has defined/categorised a particular term
Thesaurus matches: use to find terms in the index. This then allows you to select
appropriate and specific MeSH terms suitable for your search.
MeSH trees: allows you to map to and view Subject Heading hierarchies and relationships.
Note that links to Help on using the Cochrane Library are available on the Cochrane Library Home
screen.
The Subject Heading tree
The MeSH tree allows you to view where a Subject Heading is placed within the MeSH ‘tree’. The
tree illustrates the hierarchies and relationships of the different MeSH terms. You can therefore use it
to clarify and select MeSH terms.
Take for example a search on biopsy, a retrieved MeSH tree search will retrieve a list of possible
subject headings:
In the tree the nearest match will be highlighted in black. Note that there may be more than one tree
listed as the term may appear in more than one hierarchy. (If you entered a term and it is not
retrieved in the MeSH tree the Cochrane will then search for it on its MeSH Thesaurus. You can then
go through the listed thesaurus references until you find an appropriate term.)
Within a tree you can move up or down by clicking on the relevant link for the term you wish to
select. The term in this link will then be highlighted as its relationship in the tree is expanded. This
expansion may result in the non-display of some of the terms from your original tree and the
appearance of new ones relevant to this branch only.
This sheet forms part of HYMS Information Skills 3
For example, if in the illustrated search above, you decided not to select Biopsy but to click on
Endoscopy this would now appear in black as the selected term. The specific sub categories for
Endoscopy would be displayed (e.g. Angioscopy; Arthroscopy etc) but the more specific Subject Headings
indented under Biopsy (Biopsy, needle; Chorionic Villi Sampling etc) would not be displayed.
Exploding, Term only searches and Qualifiers
You will also see the following options on a retrieved Tree display:

Explode: Selects all of the terms in that tree or trees whether higher or lower in the tree
to the retrieved term. There are two options:
o Specific trees can be selected to Explode to search that tree only
o All trees can be searched by selecting the Explode All to search for all the terms
(higher or lower) shown in all the trees displayed.
N.B. The Cochrane Library MeSH Explode option therefore does not work in the same way as
the OvidSP explode option. It is therefore much more common in the Cochrane Library to
select:

Search this term only: By selecting this and any term you have highlighted this will search
against this term only and will not include all of its subcategory listings in a tree.
Once you have selected your MeSH click on the Select option. You will then see the result numbers
changing in the Search results box.

Qualifiers can be used to limit your MeSH search further. These are similar to OvidSP
Subheadings in that they are standard qualifiers which can be selected for any of the
Cochrane Library MeSH terms. More than one Subheading/Qualifier can be selected at a
time.
Once you have selected an option select Add to Search Manager to add the search to the main
search screen.
CK, last update by KW 10/13 ([email protected])
This sheet forms part of HYMS Information Skills 3