Literature searching using the PICO method


Writing a comprehensive search strategy is
a vital part of research. A good, well planned search strategy will enable you to retrieve
information specific to a topic which will help you to answer your research question.
First, ensure you have a well constructed research question. This will be a question
which has a clear objective and is neither too specific, nor too broad in scope. It will
contain key terms and concepts, for example, for health related questions, your question
may look at a research population, a condition or treatment.
In this example, our main concepts are CBT, self esteem and eating disorders.
Once you’ve identified the key concepts in your question, you can use models such
as PICO to help you break down your search. PICO is a model used in Medicine and health
which allows you to break your question down to help you plan your search. There are other
models used in different disciplines such as SPICE and ECLIPSE.
This template shows what the individual elements of PICO stand for.
Fit your key concepts into the PICO model In this example, the patient/population is
people with eating disorders (though eating disorders is the concept we will search for),
the intervention/exposure is CBT, there is no comparison and the outcome is self esteem.
The next stage is thinking up as may synonyms as possible for your concepts, that’s other
terms which may have been used by authors discussing the topic. For example, eating
disorders could also be referred to as appetite disorder, and we should also include specific
types of eating disorder here, such as bulimia and anorexia.
By including these keywords in your search you are making your search as broad as possible
and capturing as many papers as you can on the topics you’re researching.
Use techniques such as truncation and wildcards to fine tune your search.
This is a good example
of a completed PICO model for our example question
– can CBT help improve self esteem in patients with eating disorders? Truncation and wildcards
are used to fine tune the search. Search for subject headings related to your
key terms Subject heading searching involves searching
for fixed vocabulary terms which are assigned to database records to help describe article
contents. Subject headings work like ‘tags’ to classify articles.
To complete a comprehensive search, you should use subject heading searching alongside keyword
searching. To search for a subject heading in the OVID
databases such as Medline, ensure you click the ‘map term to subject heading’ box
before clicking search. This will search the database for a subject heading which most
closely matches your search term. You may find that not every keyword in your
search will have an exact match to a subject heading in the database, but if there isn’t
a match, the database will usually suggest the closest possible matching term.
This illustrates a subject tree in the database Medline.
By ticking the explode button next to a higher branch, e.g. Sports, you will include the
results tagged with the related subject headings below it as well. E.g. in this case, Athletic
performance, baseball etc. You need to decide whether you want to include
results for these sub terms as well as for the upper branch subject heading, it will
not always be appropriate to do so. If you want to just include a few subterms,
but not all of them, instead of ticking explode, tick the boxes by the individual terms separately.
The focus option narrows your search and may limit your results, so we don’t recommend
you use it if you’re doing a thorough, comprehensive search.
This provides a snapshot from a comprehensive search in Medline, you can see the keyword
searches (with .mp afterwards) and also the subject heading searches with a forward slash
after them. At the bottom you can see how the terms have been combined effectively.
The key points to remember about doing a comprehensive literature search are:
Break your search down into its key concepts, and fit them into a model such as PICO
Think of as many key terms and synonyms for each concept as you can
Use techniques such as truncation and wildcards on keyword searches (not subject heading searching)
Search for subject headings which match your key terms and incorporate them into your search
strategy

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