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A Diagnostic Test
Most radiologists will have seen articles
or heard presentations about the use of CT for diagnosis of
small bowel obstruction. Where does this fit in with the plain
film of the abdomen? Should we still be using the plain film?
Is CT better? Does ultrasound have a role? Is there any way
that we can advise the surgeon whether the patient is likely
to need surgery to relieve obstruction when we diagnose it?
There are many questions here and they
are not structured in a way that will make it easy to search
for the answers. The PICO approach allows us to formulate
a question as follows:
"In patients with Small
bowel obstruction [Patient], how does CT
[Intervention] compare with plain
films,contrast studies and ultrasound [Comparison]
for diagnosing SBO, establishing the
cause, site and grade of obstruction and in assessing the
need for urgent surgical intervention [Outcome]?"
| Patient |
Intervention |
Comparison |
Outcome |
| Small
bowel obstruction |
CT |
Plain
Films
Contrast Studies
Ultrasound |
Diagnosis
Cause
Site
Grade
Need for Surgery
|
This is a much more focused question.
In fact there are multiple focused questions, related to the
three comparative techniques and five outcomes of interest.
It also makes it easier to develop a search strategy that
will yield a smaller number of more relevant papers. Searching
is described in greater detail in another part of this site,
but for the moment it is sufficient to know that "Boolean
operators" such as "AND" and "OR"
can be used to refine a search strategy. These are fairly
intuitive concepts; when "AND" is placed between
two terms in a search strategy, the search will only return
citations that contain BOTH terms. If "OR" is used
then the search will return citations that contain EITHER
of the terms. The general principle in formulating the search
is to place "AND" between terms in each column of
the PICO table and to place "OR" between terms within
each column, as illustrated below:
| Patient |
|
Intervention |
|
Comparison |
|
Outcome |
| Small
bowel obstruction |
AND
|
CT |
AND
|
Plain
Films
OR
Contrast Studies
OR
Ultrasound |
AND
|
Diagnosis
OR
Cause
OR
Site
OR
Grade
OR
Need for Surgery |
This structured question lends itself
to a logical and repeatable search of the literature, as will
be outlined in the section on searching.
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