PRACTICE TOOLS
134
Clinical Pharmacist
May 2012
Vol 4
There are millions of studies published in the medical literature each year. Being able to identify which
ones are of the highest quality and most relevant to your own clinical practice is a useful skill to develop
How to extract the salient points
from a published clinical study
By Janice Craig, DipClinPharm,
MRPharmS
E
ach year, around six million medical
studies are published worldwide.1
Over 12,000 papers are added to the
Medline database each week. Despite this
vast amount of literature, less than 15% of
all studies published are considered to be
useful.2
Medical knowledge and practice are
changing at a fast pace; reading journals and
understanding their contents are essential
skills for practising evidence-based
medicine.
There are numerous critical appraisal
tools and guidelines available, such as the
Critical Appraisal Skills Programme (more
information is available at www.casp-uk.net),
which offer a structured approach to guide
clinicians in evaluating the validity and
weaknesses of papers. However, many of us
struggle to find sufficient time to spend
critiquing published studies.
This article offers some tips on how to
conduct a basic review of a clinical study
and identify how applicable it is to your
practice. Statistical analysis is beyond the
scope of this article.
Abstract
The abstract is intended to grab the
attention of potential readers. It is often the
first and only thing that people read
because it is usually the only part of the
paper that is electronically accessible
through search engines and freely available
from journal websites. Most abstracts tend
to be structured in the same format as the
full paper, aiming to provide a brief
summary of:
● What was studied
● Who participated
● How and where the research was
performed
● What the researchers found
At this point ask yourself: Is this study
clinically relevant? Are the subjects or is the
clinical situation similar to my patients or
IN SHORT
There are 12,000 medical studies
added to the Medline database every
week. Having a system for identifying
which are high quality and relevant to
practice is hugely beneficial.
While critical appraisal is the most
comprehensive method for assessing
clinical papers, this article suggests
some simple tips for those who have
not undergone critical appraisal training.
practice? If you find an important
conclusion in the abstract, the next step is
to check it against the study design and
findings reported in the full paper.
Primary objective and outcome
The primary objective provides the main
focus of the study and is measured by the
primary outcome, describing a component
of a participant’s clinical or functional
status after an intervention has been
applied. Current relevant clinical
knowledge is usually described in the
article and the research question should
aim to reflect and add to this.
The primary outcome is used to assess
the effectiveness of an intervention.
Important questions to consider here are:
● Are the outcomes clinically relevant
and unambiguous?
● Can the outcomes be measured for
all patients?
● How often and for how long are the
outcomes being measured (and is
this period adequate)?
● Is the primary outcome relevant to
your clinical practice?
Methods
Although most people rarely consider
study methods to be an exciting read, they
are a critical section that should provide a
clear overview and insight into how the
study was performed.
When evaluating a study’s method,
consider the following:
● Who are the study participants? Are
they representative of the patients
you see in practice? Have the
inclusion and exclusion criteria been
clearly defined?
● How were study participants chosen?
Were they randomised to reduce
selection bias? Were the participants
and the investigators blinded to the
allocation (ie, was the study openlabel, single-blind or double-blind)?
The sample size should be large
enough to answer the research
question and show any statistically
significant difference
● Is the study well designed and
suitable? What was the data
collection technique and is it
appropriate? Is the design clear
enough that it could be replicated by
other researchers?
● How were the results examined,
analysed and dealt with statistically
Vol 4
Careful attention towards these
methodological details can help to evaluate
properly the validity of what is reported in
the results section and the conclusion of
the study.
Results
When interpreting results the main
considerations are whether or not the
results are clinically important, and the size
of any potential benefit or harm. The way
the results are presented may depend on
the type of study.
When considering efficacy, ensure that
the primary outcome results are reported
clearly. Secondary outcomes may also be
important or of interest. Bear in mind that
surrogate endpoints (eg, HbA1c, change in
serum creatinine) might have been chosen
by the researchers, as opposed to clinical
outcomes such as mortality. Additionally,
beware of sub-analyses that do not form
part of the original study design. These
might be useful for generating hypotheses
for future study, but clinical decisions
based on such findings should be made
with caution.
Jeremy Allen | Dreamstime.com
Safety Confirming the efficacy of an
intervention is an important part of
evidence-based medicine, but it is vital also
to consider the safety of the intervention.
Many interventions used in everyday
clinical practice have potential benefits and
adverse consequences that need to be
weighed against each other. Consider safety
and tolerability outcomes alongside those
for efficacy. The most commonly reported
adverse effects should also be summarised,
as well as clear explanation regarding how
the adverse effect may be related to
treatment.
Are the conclusions valid?
The conclusion or discussion section is
often considered to be the most useful part
of a paper. Check whether there is a clear
introductory or summary statement about
the major findings and their clinical
importance. If this statement is missing,
what does this say about the results? It
might imply that no meaningful conclusion
was found.
The most important question to
consider is whether the results support the
initial study hypothesis — and, if not, why
not? The conclusion should offer an indepth explanation of what the researchers
determined (rather than just listing the
numbers) that is rational and justified by
the study results. Again, it is important to
consider whether there are sufficient data
to justify the conclusions that have been
drawn.
A thorough review of current relevant
literature is often included in the full
paper; does this study confirm the findings
of other published studies? Interpreting the
results and considering the clinical
relevance (ie, how much the intervention
really affected the outcome) will require
your clinical judgement. If there are any
differences between the study participants
and the general patient population for the
condition being treated, the effectiveness of
the intervention might be different in real
life so any such differences should be
discussed.
Authors often introduce possible
implications and practical applications of
their results, but beware of overspeculation.
Consider if, and how, the clinical results
may be applicable to your particular
patient population.
Limitations Regardless of experimental
design, every study has limitations; these
should be identified and a clear
explanation given about how these could
have affected the results. Did the
researchers address both the positive and
negative aspects of the study? Negative
results can be fairly common and may be
Clinical Pharmacist
played down or even left unpublished.
However, they can provide equally valuable
contributions to the advancement of
clinical knowledge if highlighted and
explained.
Finally, consider what can and cannot
be concluded from the study. This often
helps to generate questions on areas for
further research.
Funding and author declarations
The reputation of the medical journal in
which the paper is published is not enough
to guarantee that the findings have
sufficient credibility to apply in practice.
Most journals nowadays require disclosure
of research support and potential conflicts
of interest from the authors. This allows
readers to identify and consider any
potential bias that occurs from outside
funding, such as pharmaceutical company
sponsors.
This is not to say that industrysponsored studies cannot produce reliable
research. Look for assurances that the
design and results are not influenced by
any commercial association. Declarations
of interests allow for identification of
personal factors that might have biased the
findings and help to ensure that the
research is not published for personal or
institutional gain.
Summarising
In conclusion, carefully read through the
paper and then review it again to identify
sentences that specify the most important
pieces of information. Select three to five
of these sentences and summarise the main
points in your head. Consider their
relevance to your patients in clinical
practice.
The more practice you get with reading
studies of varying quality, the easier you
will find getting the salient points out of
published research.
References
1
Fletcher R, Fletcher S. Keeping clinically up-to-date.
Evidence-based approach to the medical literature.
Journal of General Internal Medicine
1997;12(Suppl):S5–14.
2
Lock S. Does editorial peer review work? Annals of
Internal Medicine 1994;121:60–1.
Janice Craig is a medicines information
pharmacist at Oxford Radcliffe
Hospitals NHS Trust.
E: [email protected]
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PRACTICE TOOLS
— eg, have all people who entered
the study been taken into account?
May 2012