4. Creating Subject Searches
There are
three steps in the construction of a subject search.
1. MeSH search
2. Keyword search
3. Combine with Boolean 'OR' operator
MeSH (Medical Subject Headings)
terms attempt to encompass all of the concepts of medicine, within a hierarchical
classification system, currently employing more than 31,000 terms. Medline articles are
indexed by at least one, and normally several MeSH terms. All decent Medline interfaces
must provide a means of translating your search into equivalent MeSH terms, and also to
allow you to choose whether you want just the MeSH term itself, or to also include some or
all of its 'children' in the MeSH hierarchy (called exploding a MeSH term). MeSH terms are
also refined by the use of Sub Headings which are broad concepts which cut across the MeSH
hierarchical tree - examples include Genetics, Epidemiology, Drug Therapy.
The creation of a subject search
will be covered in more detail when we look at the PubMed and Ovid interfaces, and there
is only a brief description below.
PubMed
performs a combined MeSH match and textword search for you automatically - for example, if
you type multiple
sclerosis into the search box, PubMed runs the search "Multiple sclerosis"[MeSH Terms] OR Multiple sclerosis[Text
Word]. Note that the
MeSH term is automatically exploded in PubMed.
The Ovid
interface allows you to combine MeSH mapping and textword searches on its Mapping Display
page. If you select the MeSH term multiple sclerosis, with Explode enabled, together with
the .mp option, this produces a search of the form exp Multiple sclerosis/ or "multiple
sclerosis".mp which is
a close equivalent to the PubMed search.
Once you have created your subject
search, you combine it with the appropriate systematic search, using the Boolean AND
operator, to answer the clinical question. |
