Welcome to the Health Sciences Library Online
Tutorial Series. This multi-part tutorial will explore the
keys to successful searching within the OVID suite of health databases, specifically Medline.
In Part 1, we will start planning a search, turning key concepts into subject headings
and adding them to the search history. OVID databases are easily accessible from
the Health Sciences Library homepage at hsl.mcmaster.ca. You will find them located under “Article
databases” in the “Key Resources” box. If you are off-campus, clicking on the OVID
link will redirect you to LibAccess where you can sign in using your MacID and password.
OVID is host to a number of different databases. Because each resource uses its own subject
headings, for the best results search one database at a time.For more information on
the coverage of each resource, click the blue icon.
For the most comprehensive search, select “OVID Medline In-Process & Other Non-Indexed
Citations, Ovid Medline Daily and OVID Medline” (1946-Present). This will redirect you to
the Medline search screen. When searching databases, we like to take
a concept-by-concept approach. The easiest way to identify key concepts is to take the
time to develop and effective search question. In real life, questions don’t typically come
in a form that is ready made for searching. Take some time to consider your information
needs. For the purposes of this tutorial, we will
try to answer the following question: “In pre-school children with food allergies, is
oral immunotherapy effective at reducing allergic sensitivity?”.
Who are we interested in? Pre-school children with food allergies.
What are we looking for? Studies of the effectiveness of oral immunotherapy.
Why are we looking for this? To help decrease sensitivity to food based allergens.
Where might we find this information? Likely in academic journal articles and the best
place to find these is in a health database like Medline. So we’re in the right place.
We will search for one term at a time, later combining these terms to construct more complex
concepts. Notice that the check box “Map Term to Subject
Heading” is selected.Many health databases use authoritative search terms called subject
headings to identify the key concepts covered in a given article. With this option selected,
the database will search for the appropriate subject headings for your concepts.
Let’s try our first concept: food allergies. Enter the concept into the search box and
click search. The suggested subject headings are listed
as blue hyperlinks. Here’s one called “Food Hypersensitivity”. Is this relevant?
Clicking on the blue “i” will take you to the subject heading’s scope note, providing
a brief definition, related subject headings, and terms that the subject heading is used
for. The subject heading “Food Hypersensitivity”
is the preferred term four our concept of food allergies. Great.
It is important to note the unique ways of navigating Medline. The OVID databases have
built-in navigation controls. Instead of using your browser’s back button, use the “Previous
Page” button to bring you back to the list of subject headings. If at any point you want
to return to the homepage, click the “Search” tab.
Medline gives you a couple of options for customizing your subject heading search.
The “Focus” check box will narrow results to articles in which “Food Hypersensitivity”
has been identified as the primary topic. Because our question deals with multiple,
equally weighted concepts, we’ll leave the focus option unchecked.
Located beside focus is the “Explode” check box. This option could be more helpful. Many
subject headings can be broken down into more specific terms. The “Explode” function allows
us to capture all of these terms in a single search.
Clicking on the subject heading “Food Hypersensitivity” takes us to Medline’s subject index, where
the database’s subject headings are arranged in a hierarchy of broader and narrower terms.
Scroll down to find our subject heading highlighted in blue.
“Food Hypersensitivity” can be exploded to include the more specific food allergies listed
below and to the right. Our question is interested in food allergies in general, so we’ll likely
want to include these narrower subject headings and their result sets. Select the “Explode”
check box and click “Continue”. This brings up a list of subheadings that
will narrow your search to articles covering specific aspects of food hypersensitivity.
These can be tempting, as they will quickly narrow a search but be careful, they will
often exclude relevant results. Click “Continue” to include all subheadings in the search.
“Food Hypersensitivity” has been added to our search history. The “exp” next to the
term tells us that the subject heading has been exploded. The number of results is also
displayed. Let’s try searching for our second concept.
Type “oral immunotherapy” into the search box and click “Search”.
Again, we are shown potential subject headings for our concept, sorted by relevance. Let’s
take a look at the scope note for “Desensitization, Immunologic”.
The “Used For” section confirms the subject heading’s relevancy but does not mention the
oral aspect of our concept directly. However, returning to the previous page, we
see a subject heading for “Administration, Oral”. Keep this term in mind, as we can use
both subject headings to manually construct our concept of oral immunotherapy.
For now, click on “Desensitization, Immunologic” to go to its place in Medline’s subject index.
Again, we’ll use the “Explode” function to include our term’s narrower subject headings.
Select the “Explode” check box and click “Continue”. Include all subheadings to ensure your search
is inclusive and click continue. The subject heading has been added as a new
line in our search history and the results are shown.
Recall, we wanted to add the subject heading “Administration, Oral” to our search. Like
our previous subject headings, we will explode the term to include more narrow subject headings
and include all subheadings in our search. At this point, we can combine the subject
headings “Desensitization, Immunologic” and “Administration, Oral” to build our concept
of oral Immunotherapy. To do this, simply click the check boxes beside each subject
heading and select “Combine selections with And” to only return results in which both
subject headings are present. This generates a fourth line in our search
history and a corresponding result set that represents our concept of oral immunotherapy.
This concludes Part 1 of the OVID Medline tutorial. We’ve identified key concepts through
question development, translated those concepts into Medline subject headings, and added these
subject headings to the search history. In Part 2, we will supplement these subject
headings with keywords, combine concepts together, and apply limits to narrow our results.